Visual representation of your height's healthy BMI zones and your current ideal weight range.
BMI Category
BMI Range
Weight Range for Your Height (kg)
Standard BMI categories and the corresponding weight ranges for your specified height.
What is Ideal Weight Range?
An ideal weight range refers to the spectrum of body weights that are considered healthy for an individual, given their height, sex, and age. It's not about a single perfect number, but rather a zone where the risk of developing weight-related health issues like heart disease, diabetes, and certain cancers is minimized. Understanding your ideal weight range is a crucial step in managing your overall health and well-being. It helps set realistic and achievable goals for weight management and provides a benchmark for assessing your current health status. Many people confuse ideal weight with the weight they might have had in their youth, or a number seen in media, but the medically accepted ideal weight range is based on scientific data and health outcomes.
Who should use it? Anyone interested in understanding their body composition and health status, including individuals looking to lose, gain, or maintain weight, athletes, healthcare professionals, and those seeking to adopt a healthier lifestyle. It's a valuable tool for self-assessment and for guiding discussions with doctors or dietitians. This calculation is particularly useful for adults, as growth and development in children and adolescents mean their healthy weight ranges are dynamic and best assessed by a pediatrician.
Common misconceptions about ideal weight include believing there's a single "magic number" that applies to everyone, or that it solely dictates overall health. Factors like muscle mass, body fat percentage, bone density, and individual metabolism also play significant roles. Furthermore, focusing solely on weight can be detrimental; a holistic approach to health that includes diet, exercise, sleep, and stress management is paramount. Another misconception is that ideal weight is purely aesthetic; in reality, it's a metric for **health risk reduction**.
Ideal Weight Range Formula and Mathematical Explanation
Calculating an ideal weight range typically involves using established formulas that consider height and biological sex. While there are various methods, the commonly referenced ones often stem from research that correlates weight with health outcomes, such as the Body Mass Index (BMI) or specific formulas like the Hamwi or Devine formulas, which are then adapted to provide a range. For this calculator, we utilize a range derived from common BMI categories (18.5 to 24.9) which are widely accepted as representing a healthy weight for adults. We also incorporate a calculation for Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, as this provides insight into energy expenditure.
BMI-Based Ideal Weight Range Calculation:
The core of this calculator relies on the Body Mass Index (BMI). BMI is a measure of body fat based on height and weight that applies to adult men and women. The formula for BMI is:
BMI = weight (kg) / height (m)^2
To find the ideal weight range, we rearrange this formula to solve for weight:
Weight (kg) = BMI * height (m)^2
A healthy BMI is generally considered to be between 18.5 and 24.9.
Therefore, the ideal weight range for a given height is calculated by plugging the lower and upper bounds of the healthy BMI into the formula:
Lower Ideal Weight (kg) = 18.5 * (height in meters)^2
Upper Ideal Weight (kg) = 24.9 * (height in meters)^2
The Mifflin-St Jeor equation is a common formula used to estimate a person's BMR, the number of calories the body needs to maintain basic functions at rest. While not directly used for the weight range, it's an important metabolic indicator.
For Men: BMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age in years) + 5
For Women: BMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age in years) - 161
Note: The calculator uses the healthy weight range to estimate a potential BMR.
Variables Table:
Variable
Meaning
Unit
Typical Range
Height
Individual's vertical measurement from floor to top of head.
Centimeters (cm)
140 – 200 cm (Adults)
Sex
Biological sex, used to adjust BMR formula.
Categorical (Male/Female)
Male, Female
Age
Individual's age in years.
Years
18 – 80 (for this calculator's BMR context)
BMI
Body Mass Index, a ratio of weight to height squared.
kg/m²
18.5 – 24.9 (Healthy Range)
Ideal Weight
The calculated weight falling within the healthy BMI range.
Formula Used: BMI-based weight range calculation and Mifflin-St Jeor for BMR.
Interpretation: For a 180 cm tall male, a weight between 60.0 kg and 80.7 kg falls within the healthy BMI range. This range suggests a lower risk for weight-related health conditions. The estimated BMR indicates the minimum calories needed daily.
Formula Used: BMI-based weight range calculation and Mifflin-St Jeor for BMR.
Interpretation: For a 162 cm tall female, maintaining a weight between 48.6 kg and 65.3 kg is considered healthy based on BMI. This range helps her set a target for weight management, potentially aiming for the middle of the range if current weight is outside it. The BMR suggests her resting metabolic rate is around 1197 calories.
How to Use This Ideal Weight Range Calculator
Enter Your Height: Input your height in centimeters (e.g., 175 for 1.75 meters). Accurate height measurement is crucial for correct calculations.
Select Your Biological Sex: Choose 'Male' or 'Female' from the dropdown menu. This affects the BMR calculation.
Enter Your Age: Input your age in years. Age is also used in the BMR calculation.
Calculate: Click the "Calculate" button. The results will update instantly.
Read Your Results:
Primary Result: This shows your calculated ideal weight range in kilograms.
Healthy BMI Range: Displays the standard BMI values (18.5-24.9) that define a healthy weight.
Estimated BMR: This indicates the approximate number of calories your body burns at rest.
Weight Range for Your Height (kg): The table provides specific weight ranges corresponding to different BMI categories for your height.
Interpret the Results: Compare your current weight to the calculated ideal weight range. If you are outside this range, consider consulting a healthcare professional or registered dietitian to discuss a safe and effective weight management plan. Remember that muscle mass can affect weight, and BMI is a screening tool, not a definitive diagnosis.
Use the Buttons:
Reset: Clears all fields and restores default values, allowing you to start over.
Copy Results: Copies the main result, intermediate values, and key assumptions to your clipboard for easy sharing or note-taking.
This calculator is a tool to provide guidance. Always consult with a healthcare provider for personalized health advice.
Key Factors That Affect Ideal Weight Results
While height and sex are primary inputs for calculating an ideal weight range using BMI, several other factors significantly influence an individual's actual healthy weight and overall body composition. These factors mean that the calculated range is a guideline, not an absolute prescription.
Body Composition (Muscle vs. Fat): Muscle is denser than fat. An individual with a high muscle mass might weigh more than someone of the same height and sex who has less muscle and more body fat, yet still be considered healthy. BMI doesn't distinguish between muscle and fat, so a very muscular person could register as "overweight" by BMI standards despite having a low body fat percentage. This is why focusing solely on weight can be misleading.
Bone Density and Frame Size: People naturally have different bone structures and densities. Someone with a larger bone frame might naturally weigh more than someone with a smaller frame, even if they have similar body composition. While difficult to quantify precisely without medical assessment, frame size can influence where an individual falls within their ideal weight range.
Metabolism and Genetics: Individual metabolic rates vary considerably. Some people naturally burn calories faster than others due to genetics and physiological differences. This can affect how easily weight is gained or lost and where an individual's healthy weight naturally sits, even within the standard BMI guidelines.
Age-Related Changes: As people age, body composition often changes. Muscle mass can decrease, and body fat may increase, even if total weight remains stable. Metabolism also tends to slow down. While the calculator uses age for BMR, the body's response to weight and its health implications can shift with decades of life.
Activity Level: A highly active individual, especially one engaging in strength training, will likely have more muscle mass. Conversely, a sedentary individual may have less muscle and potentially more body fat. The ideal weight range calculation doesn't account for lifestyle directly, but it's a critical consideration when interpreting the results and setting health goals. A physically active person might thrive at the higher end of the ideal weight range due to muscle.
Hormonal Factors and Medical Conditions: Certain hormonal imbalances (e.g., thyroid issues, PCOS) or medical conditions can significantly impact weight regulation, metabolism, and body composition. Medications prescribed for various conditions can also lead to weight gain or loss as a side effect. These require personalized medical management rather than relying solely on a general calculator.
Dietary Habits and Nutrition: While not directly factored into the ideal weight *range* calculation itself, eating patterns and the quality of nutrition are paramount to achieving and maintaining a healthy weight. A balanced diet supports muscle health, energy levels, and overall well-being, influencing how one feels and performs at any given weight.
Frequently Asked Questions (FAQ)
Q1: Is the ideal weight range the same for everyone of the same height and sex?
A1: The calculated ideal weight range (based on BMI) provides a general guideline. However, individual factors like muscle mass, bone density, and metabolism mean that not everyone within that range will have the same body composition or health status. It's a starting point for assessing health, not a definitive measure.
Q2: Can I use this calculator if I'm pregnant or breastfeeding?
A2: No. Pregnancy and breastfeeding significantly alter body weight and composition. This calculator is designed for non-pregnant adults. Consult your healthcare provider for weight guidance during these periods.
Q3: What if my current weight is outside the ideal weight range?
A3: If your weight is above or below the calculated range, it indicates a potential health risk. It's advisable to consult with a doctor or a registered dietitian. They can help you understand the underlying reasons and create a personalized, safe plan for weight management or adjustment.
Q4: How accurate is the BMI calculation for athletes?
A4: BMI can be less accurate for individuals with very high muscle mass, such as athletes. Due to muscle's density, they might have a high BMI even if their body fat percentage is low and they are very healthy. In such cases, body fat percentage measurements provide a more nuanced view of health.
Q5: Does age really affect ideal weight?
A5: Age is primarily used in the BMR calculation, which estimates calorie needs. While the healthy BMI range itself doesn't change with age for adults, metabolic rate and body composition typically do. This means achieving or maintaining a weight within the ideal range might require different approaches at different life stages.
Q6: Should I aim for the middle of the ideal weight range?
A6: Aiming for the middle of the ideal weight range is often a good general goal, as it typically represents a lower risk profile. However, the "best" weight is highly individual. If you are already within the range and feel healthy and energetic, there may be no need to adjust.
Q7: What's the difference between ideal weight and healthy weight?
A7: These terms are often used interchangeably. "Ideal weight" can sometimes imply a single target, whereas "healthy weight range" emphasizes a spectrum of weights associated with good health outcomes and reduced disease risk. Our calculator provides a range.
Q8: How often should I check my ideal weight range?
A8: Your height doesn't change significantly after adulthood, so your ideal weight range (based on BMI) remains constant. However, it's beneficial to monitor your actual weight periodically (e.g., monthly) and assess how it aligns with the range, paying attention to changes in your body composition and overall health.
Healthy Eating Guide: Learn about balanced nutrition for weight management and overall health.
Exercise Planner: Create a workout routine to support your health and fitness goals.
var chartInstance = null; // Global variable to hold the chart instance
function validateInput(id, min, max, errorMessageId, isRequired = true) {
var element = document.getElementById(id);
var errorElement = document.getElementById(errorMessageId);
var value = parseFloat(element.value);
if (errorElement) {
errorElement.textContent = ";
}
if (isRequired && (element.value === null || element.value.trim() === ")) {
if (errorElement) errorElement.textContent = 'This field is required.';
return false;
}
if (!isNaN(value)) {
if (value max) {
if (errorElement) errorElement.textContent = 'Value cannot be greater than ' + max + '.';
return false;
}
} else if (isRequired) {
if (errorElement) errorElement.textContent = 'Please enter a valid number.';
return false;
}
return true;
}
function calculateIdealWeight() {
var heightCm = document.getElementById("heightCm");
var age = document.getElementById("age");
var sex = document.getElementById("sex").value;
var resultDiv = document.getElementById("result");
var mainResultDiv = document.getElementById("mainResult");
var bmiRangeDiv = document.getElementById("bmiRange");
var bmrDiv = document.getElementById("bmr");
var idealWeightMetricDiv = document.getElementById("idealWeightMetric");
var formulaExplanationDiv = document.getElementById("result").querySelector(".formula-explanation");
var bmiTableBody = document.getElementById("bmiTableBody");
var isValid = true;
isValid = validateInput("heightCm", 100, 250, "heightCmError") && isValid; // Min height 1m, Max height 2.5m
isValid = validateInput("age", 1, 120, "ageError") && isValid; // Min age 1, Max age 120
if (!isValid) {
resultDiv.style.display = "none";
return;
}
var heightCmValue = parseFloat(heightCm.value);
var ageValue = parseFloat(age.value);
var heightM = heightCmValue / 100;
var heightM2 = heightM * heightM;
// Constants for healthy BMI range
var lowerBmi = 18.5;
var upperBmi = 24.9;
// Calculate ideal weight range
var lowerIdealWeightKg = lowerBmi * heightM2;
var upperIdealWeightKg = upperBmi * heightM2;
// Calculate BMR using Mifflin-St Jeor equation (requires current weight, so we'll estimate using mid-range)
var avgIdealWeightKg = (lowerIdealWeightKg + upperIdealWeightKg) / 2;
var bmrKcal = 0;
if (sex === "male") {
bmrKcal = (10 * avgIdealWeightKg) + (6.25 * heightCmValue) – (5 * ageValue) + 5;
} else { // female
bmrKcal = (10 * avgIdealWeightKg) + (6.25 * heightCmValue) – (5 * ageValue) – 161;
}
bmrKcal = Math.max(0, bmrKcal); // Ensure BMR is not negative
// Format results
var formattedLowerWeight = lowerIdealWeightKg.toFixed(1);
var formattedUpperWeight = upperIdealWeightKg.toFixed(1);
var formattedBmr = bmrKcal.toFixed(0);
mainResultDiv.innerHTML = "Ideal Weight Range: " + formattedLowerWeight + " kg – " + formattedUpperWeight + " kg";
bmiRangeDiv.innerHTML = "Healthy BMI: " + lowerBmi.toFixed(1) + " – " + upperBmi.toFixed(1);
bmrDiv.innerHTML = "Estimated BMR: " + formattedBmr + " kcal/day";
idealWeightMetricDiv.innerHTML = "Based on height (" + heightCmValue + " cm) and sex (" + sex + ").";
formulaExplanationDiv.innerHTML = "The ideal weight range is calculated using a healthy Body Mass Index (BMI) range of 18.5-24.9. The Basal Metabolic Rate (BMR) is estimated using the Mifflin-St Jeor equation with an average ideal weight for your height.";
resultDiv.style.display = "flex";
// Populate BMI Table
bmiTableBody.innerHTML = "; // Clear existing rows
var bmiCategories = [
{ label: "Underweight", bmi: 18.5, type: "lower" },
{ label: "Healthy Weight", bmi: 24.9, type: "upper" },
{ label: "Overweight", bmi: 29.9, type: "upper" },
{ label: "Obese Class I", bmi: 34.9, type: "upper" },
{ label: "Obese Class II", bmi: 39.9, type: "upper" },
{ label: "Obese Class III", bmi: Infinity, type: "upper" }
];
var startBmi = 0;
var startWeight = 0;
for (var i = 0; i 0) {
// This is the lower bound of a range, handled by the previous category's upper bound
// We only care about the start of the current category
}
var row = bmiTableBody.insertRow();
var cell1 = row.insertCell(0);
var cell2 = row.insertCell(1);
var cell3 = row.insertCell(2);
cell1.textContent = category.label;
cell2.textContent = (startBmi === 0 ? " 0 ? startBmi.toFixed(1) + " – " : "") ) + (endBmi === Infinity ? "" : endBmi.toFixed(1));
cell3.textContent = (startWeight === 0 ? " 0 ? startWeight.toFixed(1) + " – " : "") ) + (endWeight === Infinity ? "> " + (upperIdealWeightKg * 1.5).toFixed(1) : endWeight.toFixed(1)); // Arbitrary large number for Infinity
// Update start values for the next iteration
startBmi = endBmi;
startWeight = endWeight;
if (endBmi === Infinity) { // Prevent calculating for infinity further
startBmi = Infinity;
startWeight = Infinity;
}
}
// Update Chart
updateChart(heightM2, lowerIdealWeightKg, upperIdealWeightKg);
}
function updateChart(heightM2, lowerIdealWeightKg, upperIdealWeightKg) {
var ctx = document.getElementById('weightRangeChart').getContext('2d');
// Define weight ranges for different BMI levels based on height
var weightRanges = [
{ bmi: 16.5, label: 'Underweight (Severe)', color: '#ffc107' }, // Lower end of underweight
{ bmi: 18.5, label: 'Underweight (Mild)', color: '#ffea00' }, // Start of healthy
{ bmi: 24.9, label: 'Healthy Weight', color: '#28a745' }, // End of healthy
{ bmi: 29.9, label: 'Overweight', color: '#fd7e14' }, // Start of overweight
{ bmi: 34.9, label: 'Obese Class I', color: '#e67e22' }, // Start of obese I
{ bmi: 39.9, label: 'Obese Class II', color: '#dc3545' }, // Start of obese II
{ bmi: 40.0, label: 'Obese Class III', color: '#a70000' } // Start of obese III
];
var chartData = {
labels: [],
datasets: [{
label: 'Healthy Weight Range',
data: [],
backgroundColor: 'rgba(40, 167, 69, 0.6)', // Green for healthy
borderColor: 'rgba(40, 167, 69, 1)',
borderWidth: 1,
order: 2 // Rendered on top
}, {
label: 'Weight for BMI Categories',
data: [],
backgroundColor: [], // Will be set dynamically
borderColor: [], // Will be set dynamically
borderWidth: 1,
order: 1 // Rendered below
}]
};
// Calculate weights for each BMI category and populate datasets
var currentMinWeight = 0;
var currentMaxWeight = 0;
var currentLabelStart = 0;
for (var i = 0; i < weightRanges.length; i++) {
var range = weightRanges[i];
var weight = range.bmi * heightM2;
if (range.bmi === 18.5) { // Special handling for the start of healthy range
chartData.datasets[0].data.push({ x: range.bmi, y: weight });
chartData.datasets[0].label = `Healthy Weight (${range.bmi.toFixed(1)} – ${weightRanges[i+1]?.bmi.toFixed(1) ?? 'N/A'})`;
currentMinWeight = weight;
currentLabelStart = range.bmi;
} else if (range.bmi === 24.9) { // Special handling for the end of healthy range
chartData.datasets[0].data.push({ x: range.bmi, y: weight });
currentMaxWeight = weight;
// Add a placeholder to ensure the line goes up to this point
if (i + 1 < weightRanges.length) {
chartData.datasets[1].data.push({ x: range.bmi, y: weight });
chartData.datasets[1].backgroundColor.push(range.color);
chartData.datasets[1].borderColor.push(range.color.replace('0.6', '1'));
}
chartData.labels.push(`${currentLabelStart.toFixed(1)} – ${range.bmi.toFixed(1)}`);
} else {
chartData.datasets[1].data.push({ x: range.bmi, y: weight });
chartData.datasets[1].backgroundColor.push(range.color);
chartData.datasets[1].borderColor.push(range.color.replace('0.6', '1'));
if (i ${weightRanges[i-1].bmi.toFixed(1)}`);
}
}
}
// Add the lower bound of underweight as the first point for dataset 1
chartData.datasets[1].data.unshift({ x: 0, y: 0 }); // Start from 0 height for context
chartData.datasets[1].backgroundColor.unshift('rgba(255, 193, 7, 0.6)'); // Underweight color
chartData.datasets[1].borderColor.unshift('rgba(255, 193, 7, 1)');
chartData.labels.unshift(' r.bmi === 40.0).bmi * heightM2;
var obese3Weight = 40.0 * heightM2;
chartData.datasets[1].data.push({ x: 40.0, y: obese3Weight }); // Representing the start of Obese III
chartData.datasets[1].backgroundColor.push('#a70000');
chartData.datasets[1].borderColor.push('#a70000');
// Add the ideal weight range as a distinct line/band on the chart
// This requires a different approach, maybe just showing it as a highlighted region on the Y-axis for the specific height
// For simplicity, we'll represent it as a single point/line for the calculated range.
// A better chart might show a bar for the specific height's range.
// Let's update dataset[0] to represent the calculated range more clearly.
chartData.datasets[0].data = [
{ x: 18.5, y: lowerIdealWeightKg },
{ x: 24.9, y: upperIdealWeightKg }
];
chartData.datasets[0].label = `Your Ideal Weight Range (${lowerIdealWeightKg.toFixed(1)}kg – ${upperIdealWeightKg.toFixed(1)}kg)`;
// Update chart if it exists, otherwise create it
if (chartInstance) {
chartInstance.destroy(); // Destroy previous chart instance
}
chartInstance = new Chart(ctx, {
type: 'line', // Use line chart to show ranges
data: chartData,
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
x: {
title: {
display: true,
text: 'BMI Category',
font: {
size: 14
}
},
ticks: {
callback: function(value, index, ticks) {
// Use labels array for x-axis ticks
return chartData.labels[index];
}
}
},
y: {
title: {
display: true,
text: 'Weight (kg)',
font: {
size: 14
}
},
beginAtZero: true,
suggestedMax: Math.max(upperIdealWeightKg * 1.5, 150) // Scale Y-axis appropriately
}
},
plugins: {
title: {
display: true,
text: 'Weight Ranges by BMI for Your Height',
font: {
size: 16
}
},
legend: {
display: true,
position: 'bottom'
},
tooltip: {
callbacks: {
title: function(tooltipItems) {
return `BMI: ${tooltipItems[0].parsed.x.toFixed(1)}`;
},
label: function(tooltipItem) {
var datasetLabel = tooltipItem.dataset.label || ";
var value = tooltipItem.parsed.y.toFixed(1);
return datasetLabel + ': ' + value + ' kg';
}
}
}
}
}
});
}
function resetCalculator() {
document.getElementById("heightCm").value = "";
document.getElementById("sex").value = "male";
document.getElementById("age").value = "";
document.getElementById("result").style.display = "none";
document.getElementById("heightCmError").textContent = "";
document.getElementById("ageError").textContent = "";
if (chartInstance) {
chartInstance.destroy();
chartInstance = null;
}
document.getElementById("bmiTableBody").innerHTML = ";
}
function copyResults() {
var mainResult = document.getElementById("mainResult").innerText;
var bmiRange = document.getElementById("bmiRange").innerText;
var bmr = document.getElementById("bmr").innerText;
var metric = document.getElementById("idealWeightMetric").innerText;
var formula = document.querySelector("#result .formula-explanation").innerText;
var textToCopy = mainResult + "\n" +
bmiRange + "\n" +
bmr + "\n" +
metric + "\n" +
"\nAssumptions:\n" + formula;
navigator.clipboard.writeText(textToCopy).then(function() {
// Success message or visual feedback could be added here
alert("Results copied to clipboard!");
}, function(err) {
// Error handling
console.error("Could not copy text: ", err);
alert("Failed to copy results. Please copy manually.");
});
}
// Initial calculation on page load if values are present (e.g., from saved state or URL params)
// For a simple implementation, we can trigger calculate on load if default values make sense or are set.
// Let's set some default sensible values for demonstration, or rely on user input.
// document.addEventListener('DOMContentLoaded', function() {
// document.getElementById("heightCm").value = 170;
// document.getElementById("age").value = 30;
// calculateIdealWeight(); // Initial calculation
// });
// Add event listeners for real-time updates on input change
document.getElementById("heightCm").addEventListener("input", calculateIdealWeight);
document.getElementById("sex").addEventListener("change", calculateIdealWeight);
document.getElementById("age").addEventListener("input", calculateIdealWeight);
// Small chart library for rendering
// Basic Chart.js compatibility check (assuming Chart.js is available globally or embedded)
// If not using a library, you'd have to implement native canvas drawing here.
// For this example, we'll assume a basic Chart.js functionality if available,
// otherwise, this script needs a full canvas drawing implementation.
// Since the prompt requires NO external libraries, we must use native canvas or SVG.
// Let's implement a basic native canvas drawing for the chart.
// — Native Canvas Chart Implementation —
// Destroy existing chartInstance if it was initialized by a library before this script runs
if (chartInstance) {
chartInstance.destroy();
}
// Function to draw the chart using native canvas API
function drawNativeChart() {
var canvas = document.getElementById('weightRangeChart');
if (!canvas) return;
var ctx = canvas.getContext('2d');
canvas.width = canvas.parentElement.offsetWidth * 0.9; // Responsive width
canvas.height = 300; // Fixed height for now
ctx.clearRect(0, 0, canvas.width, canvas.height); // Clear previous drawing
// Get calculated values from the calculator
var heightCmInput = document.getElementById("heightCm");
var sexInput = document.getElementById("sex");
var ageInput = document.getElementById("age");
var heightCmValue = parseFloat(heightCmInput.value);
var sex = sexInput.value;
// Basic validation to ensure calculation can proceed
if (isNaN(heightCmValue) || heightCmValue <= 0) {
ctx.font = '16px Arial';
ctx.fillStyle = '#dc3545';
ctx.textAlign = 'center';
ctx.fillText('Enter valid height to see chart.', canvas.width / 2, canvas.height / 2);
return;
}
var heightM = heightCmValue / 100;
var heightM2 = heightM * heightM;
var lowerBmi = 18.5;
var upperBmi = 24.9;
var lowerIdealWeightKg = lowerBmi * heightM2;
var upperIdealWeightKg = upperBmi * heightM2;
// Define BMI categories and corresponding weight ranges for the given height
var bmiCategories = [
{ bmi: 16.5, label: 'Underweight (Severe)', color: '#ffc107' },
{ bmi: 18.5, label: 'Underweight (Mild)', color: '#ffea00' },
{ bmi: 24.9, label: 'Healthy Weight', color: '#28a745' },
{ bmi: 29.9, label: 'Overweight', color: '#fd7e14' },
{ bmi: 34.9, label: 'Obese Class I', color: '#e67e22' },
{ bmi: 39.9, label: 'Obese Class II', color: '#dc3545' },
{ bmi: 40.0, label: 'Obese Class III', color: '#a70000' }
];
// Calculate max weight for scaling
var maxWeight = upperIdealWeightKg * 1.8; // Scale Y-axis based on upper ideal weight
if (isNaN(maxWeight) || maxWeight <= 0) maxWeight = 150; // Default max weight if calculation fails
// Define chart area and margins
var margin = { top: 30, right: 20, bottom: 70, left: 60 };
var chartWidth = canvas.width – margin.left – margin.right;
var chartHeight = canvas.height – margin.top – margin.bottom;
// Draw background and title
ctx.fillStyle = '#ffffff';
ctx.fillRect(margin.left, margin.top, chartWidth, chartHeight);
ctx.font = 'bold 16px Arial';
ctx.fillStyle = '#004a99';
ctx.textAlign = 'center';
ctx.fillText('Weight Ranges by BMI for Your Height', canvas.width / 2, margin.top / 2);
// Draw X-axis (BMI Categories)
ctx.strokeStyle = '#cccccc';
ctx.lineWidth = 1;
ctx.beginPath();
ctx.moveTo(margin.left, margin.top + chartHeight);
ctx.lineTo(margin.left + chartWidth, margin.top + chartHeight);
ctx.stroke();
// Draw Y-axis (Weight in kg)
ctx.beginPath();
ctx.moveTo(margin.left, margin.top);
ctx.lineTo(margin.left, margin.top + chartHeight);
ctx.stroke();
// Y-axis labels and ticks
var yTicks = 5;
var yTickSpacing = chartHeight / yTicks;
ctx.font = '12px Arial';
ctx.fillStyle = '#333333';
ctx.textAlign = 'right';
for (var i = 0; i <= yTicks; i++) {
var y = margin.top + chartHeight – (i * yTickSpacing);
var value = (i / yTicks) * maxWeight;
ctx.fillText(value.toFixed(0), margin.left – 10, y + 5);
ctx.beginPath();
ctx.moveTo(margin.left – 5, y);
ctx.lineTo(margin.left, y);
ctx.stroke();
}
ctx.fillText('Weight (kg)', margin.left – 40, margin.top + chartHeight / 2);
// Draw BMI category blocks and labels
ctx.textAlign = 'center';
var xTickWidth = chartWidth / bmiCategories.length;
var currentX = margin.left;
for (var i = 0; i < bmiCategories.length; i++) {
var category = bmiCategories[i];
var weight = category.bmi * heightM2;
if (isNaN(weight) || weight c.bmi === 18.5) * xTickWidth);
var healthyEndX = margin.left + (bmiCategories.findIndex(c => c.bmi === 24.9) * xTickWidth) + xTickWidth; // End of the 'Healthy Weight' block
var healthyTopY = margin.top + chartHeight – (upperIdealWeightKg / maxWeight) * chartHeight;
var healthyBottomY = margin.top + chartHeight – (lowerIdealWeightKg / maxWeight) * chartHeight;
ctx.fillRect(healthyStartX, healthyTopY, healthyEndX – healthyStartX, healthyBottomY – healthyTopY);
// Draw the ideal weight range line for the specific height
ctx.strokeStyle = '#004a99';
ctx.lineWidth = 3;
ctx.beginPath();
var lowerIdealX = margin.left + (bmiCategories.findIndex(c => c.bmi === 18.5) * xTickWidth) + (xTickWidth / 2); // Center of Healthy Weight block
var upperIdealX = margin.left + (bmiCategories.findIndex(c => c.bmi === 24.9) * xTickWidth) + (xTickWidth / 2); // Center of Healthy Weight block
// Find the actual BMI values for the start and end of the calculated range
var bmiForLowerWeight = 18.5;
var bmiForUpperWeight = 24.9;
// Calculate the X position for these BMI values within the chart width
// This requires mapping BMI values to pixel positions.
// For simplicity, let's draw a thicker line across the healthy range for this height.
ctx.moveTo(healthyStartX, healthyTopY);
ctx.lineTo(healthyEndX, healthyTopY); // Draw top line of range
ctx.moveTo(healthyStartX, healthyBottomY);
ctx.lineTo(healthyEndX, healthyBottomY); // Draw bottom line of range
ctx.moveTo(healthyStartX, (healthyTopY + healthyBottomY) / 2);
ctx.lineTo(healthyEndX, (healthyTopY + healthyBottomY) / 2); // Draw middle line
ctx.stroke();
// Add legend text for the ideal weight range
ctx.fillStyle = '#004a99′;
ctx.font = '12px Arial';
ctx.textAlign = 'left';
ctx.fillText(`Your Ideal Range (${lowerIdealWeightKg.toFixed(1)}kg – ${upperIdealWeightKg.toFixed(1)}kg)`, healthyEndX + 10, (healthyTopY + healthyBottomY) / 2);
}
// Call drawNativeChart when the page loads and when inputs change
document.addEventListener('DOMContentLoaded', drawNativeChart);
document.getElementById("heightCm").addEventListener("input", drawNativeChart);
document.getElementById("sex").addEventListener("change", drawNativeChart); // Sex doesn't affect chart directly but recalculation is needed
document.getElementById("age").addEventListener("input", drawNativeChart); // Age doesn't affect chart directly but recalculation is needed