Professional Ideal Body Weight (IBW) & BMI Analysis Tool
Male
Female
Gender affects formula constants for ideal weight calculation.
Enter your height in centimeters.
Please enter a valid height (50-300 cm).
Enter your current weight in kilograms.
Please enter a valid weight (2-500 kg).
Age helps contextualize health data.
Please enter a valid age.
Estimated Ideal Body Weight
66.5 – 71.5 kg
Current BMI
22.9
BMI Status
Normal
Difference from Ideal
-1.5 kg
*Calculation based on the Modified Devine Formula and WHO BMI classifications.
Comparison of Ideal Weight Formulas
Differing medical formulas for height of 175 cm
Formula Name
Estimated Ideal Weight (kg)
Description
Visual Weight Analysis
Figure 1: Comparison of your current weight against standard BMI categories relative to your height.
What is a Weight Calculator in CM and KG?
A weight calculator in cm and kg is a specialized digital tool used to determine the optimal body mass for an individual based on metric measurements. Unlike generic scales, this calculator uses established medical algorithms to interpret the relationship between height (in centimeters) and mass (in kilograms) to provide a target weight range known as Ideal Body Weight (IBW).
This tool is designed for health-conscious individuals, fitness enthusiasts, and medical professionals who need precise metric assessments. It helps answer the fundamental question: "How much should I weigh for my height?" by filtering out the guesswork associated with subjective visual assessments.
Who should use this calculator?
Individuals monitoring their health journey using the metric system.
Athletes requiring specific weight-to-height ratios.
Patients following medical advice to reach a healthy BMI range.
Common Misconceptions: Ideally, one specific number represents "health." In reality, a healthy weight is a range. Muscle mass, bone density, and age play significant roles, which is why this calculator provides a bracket rather than a single digit.
Weight Calculator Formula and Mathematical Explanation
To determine the ideal weight in cm and kg, several formulas are used in the medical field. The most widely accepted method for general purpose is the Devine Formula, originally developed in 1974 to calculate dosage for medications but now standard for weight assessment.
The Logic Behind the Math
The core concept calculates a base weight for a standard height of 5 feet (152.4 cm) and adds a specific amount of kilograms for every inch (2.54 cm) above that baseline.
1. Devine Formula (Metric Adaptation)
Men: 50 kg + 2.3 kg per inch over 5 feet
Women: 45.5 kg + 2.3 kg per inch over 5 feet
2. Body Mass Index (BMI) Formula
BMI is a separate metric used to categorize weight status.
BMI = Weight (kg) / (Height (m))²
Variables Table
Key Variables in Weight Calculations
Variable
Meaning
Unit
Typical Range
H
Height
cm / m
140 – 210 cm
W
Current Weight
kg
40 – 150 kg
Base
Baseline Mass
kg
45.5 – 50 kg
Factor
Weight per unit height
kg/inch
2.3 kg
Practical Examples (Real-World Use Cases)
Example 1: The Average Male Profile
Scenario: John is 180 cm tall and weighs 85 kg. He wants to know his ideal weight.
Input Height: 180 cm (approx 5ft 11in).
Calculation: Height over 5ft is 11 inches.
Formula: 50 + (2.3 × 11) = 50 + 25.3 = 75.3 kg.
Result: John's ideal weight is roughly 75.3 kg. At 85 kg, he is above his specific IBW, though muscle mass should be considered.
Example 2: The Petite Female Profile
Scenario: Sarah is 158 cm tall and weighs 50 kg.
Input Height: 158 cm (approx 5ft 2in).
Calculation: Height over 5ft is 2 inches.
Formula: 45.5 + (2.3 × 2) = 45.5 + 4.6 = 50.1 kg.
Result: Sarah is almost exactly at her algorithmic ideal weight of 50.1 kg, indicating a balanced metric profile.
How to Use This Weight Calculator in CM and KG
Maximizing the utility of this tool requires precise inputs. Follow these steps for the best results:
Measure Accurately: Measure your height barefoot against a flat wall. Record the number in centimeters.
Select Gender: Choose biological sex, as bone density and muscle mass distribution assumptions differ between men and women in the algorithm.
Input Current Weight: Weigh yourself in the morning before eating for the most consistent kilogram value.
Review the Analysis: Look at the "Ideal Weight Range" and the "BMI Status" to understand where you fall on the spectrum.
Use the Copy Function: Click "Copy Results" to save your data for your medical records or fitness journal.
Decision Making: If your result shows "Overweight" or "Underweight," do not panic. Use this as a baseline to consult a nutritionist or doctor.
Key Factors That Affect Weight Results
While a weight calculator in cm and kg provides a scientific baseline, several biological and lifestyle factors influence the "real" ideal number.
1. Muscle Mass vs. Fat
Muscle tissue is denser than fat tissue. An athlete with high muscle mass may weigh more than the calculator's suggestion but still be metabolically healthy.
2. Bone Frame Size
Formulas often assume a medium frame. People with larger bone structures (wrist circumference > 7 inches) naturally weigh more, often 10% above the standard IBW.
3. Age and Metabolism
As we age, metabolism slows, and muscle mass tends to decrease. The "ideal" weight might shift slightly higher in older adults to provide nutritional reserves.
4. Gender Differences
Men typically have more lean mass than women of the same height, which is why the base calculation differs (50kg vs 45.5kg).
5. Hydration Levels
Daily weight fluctuates by 1-2 kg based on water retention, salt intake, and hydration. Never treat a single weigh-in as definitive.
6. Health Conditions
Conditions like thyroid issues or edema can skew weight independently of body fat. A calculator cannot diagnose these medical factors.
Frequently Asked Questions (FAQ)
Is the weight calculator in cm and kg accurate for children?
No. This calculator applies to adults (18+). Children and teenagers require specialized growth charts (percentiles) because their height and weight relationship changes rapidly during development.
Why does the result differ from my gym's scanner?
Gym scanners (bioimpedance) measure body composition (fat vs muscle). This calculator uses statistical averages based on height. Both are useful but measure different things.
What if I am very tall or very short?
The Devine and Robinson formulas are most accurate for heights between 152cm and 190cm. Extreme heights may see skewed results, where BMI becomes a more reliable secondary check.
Can I use this calculator for weight loss goals?
Yes. The "Ideal Body Weight" provides a scientifically supported target to aim for, ensuring you don't set unrealistic or unhealthy goals.
Does this calculator measure body fat percentage?
No. It calculates mass relative to height. To measure body fat percentage, you need calipers or a DEXA scan.
How often should I check my weight?
Weekly checks are recommended over daily checks to smooth out fluctuations caused by hydration and digestion.
What is the "Healthy BMI" range?
According to the WHO, a healthy BMI falls between 18.5 and 24.9. This calculator highlights if you fall outside this specific range.
Why are there different formulas (Devine, Robinson, Miller)?
Researchers developed different algorithms over decades to refine accuracy. Devine is standard, but Robinson is often used for slightly different body types. We display multiple to give a broader perspective.
Related Tools and Internal Resources
Explore our other health and financial planning tools designed to assist your lifestyle decisions:
// Global State Variables
var genderInput = document.getElementById('gender');
var heightInput = document.getElementById('height');
var weightInput = document.getElementById('currentWeight');
var ageInput = document.getElementById('age');
// Result Elements
var idealWeightDisplay = document.getElementById('idealWeightResult');
var bmiDisplay = document.getElementById('bmiResult');
var statusDisplay = document.getElementById('statusResult');
var diffDisplay = document.getElementById('diffResult');
var tableBody = document.getElementById('formulaTableBody');
var tableHeightCaption = document.getElementById('tableHeightCaption');
var chartCanvas = document.getElementById('weightChart');
// Canvas Context
var ctx = chartCanvas.getContext('2d');
// Initialize
window.onload = function() {
calculateWeight();
};
function calculateWeight() {
// Get values
var gender = genderInput.value;
var height = parseFloat(heightInput.value);
var weight = parseFloat(weightInput.value);
var age = parseFloat(ageInput.value);
// Reset errors
document.getElementById('heightError').style.display = 'none';
document.getElementById('weightError').style.display = 'none';
document.getElementById('ageError').style.display = 'none';
// Validate
var isValid = true;
if (isNaN(height) || height 300) {
document.getElementById('heightError').style.display = 'block';
isValid = false;
}
if (isNaN(weight) || weight 500) {
document.getElementById('weightError').style.display = 'block';
isValid = false;
}
if (isNaN(age) || age 120) {
// Soft validation for age as it doesn't break formulas
}
if (!isValid) return;
// update captions
tableHeightCaption.innerText = height;
// — Core Calculations —
// 1. BMI Calculation
// BMI = kg / m^2
var heightInMeters = height / 100;
var bmi = weight / (heightInMeters * heightInMeters);
// 2. Ideal Body Weight Formulas (Height in Inches needed for Devine/Robinson)
// 1 inch = 2.54 cm. Base height 5ft = 60 inches = 152.4 cm.
var heightInInches = height / 2.54;
var inchesOver60 = heightInInches – 60;
if (inchesOver60 < 0) inchesOver60 = 0; // Handle heights under 5ft gracefully for these specific formulas
var devine = 0;
var robinson = 0;
var miller = 0;
var hamwi = 0;
if (gender === 'male') {
// Devine: 50kg + 2.3kg per inch over 5ft
devine = 50 + (2.3 * inchesOver60);
// Robinson: 52kg + 1.9kg per inch over 5ft
robinson = 52 + (1.9 * inchesOver60);
// Miller: 56.2kg + 1.41kg per inch over 5ft
miller = 56.2 + (1.41 * inchesOver60);
// Hamwi: 48kg + 2.7kg per inch over 5ft
hamwi = 48 + (2.7 * inchesOver60);
} else {
// Devine: 45.5kg + 2.3kg per inch over 5ft
devine = 45.5 + (2.3 * inchesOver60);
// Robinson: 49kg + 1.7kg per inch over 5ft
robinson = 49 + (1.7 * inchesOver60);
// Miller: 53.1kg + 1.36kg per inch over 5ft
miller = 53.1 + (1.36 * inchesOver60);
// Hamwi: 45.5kg + 2.2kg per inch over 5ft
hamwi = 45.5 + (2.2 * inchesOver60);
}
// Logic for "Ideal Range": Take min and max of the calculated standard formulas
var formulas = [devine, robinson, miller, hamwi];
var minIdeal = Math.min.apply(null, formulas);
var maxIdeal = Math.max.apply(null, formulas);
// Adjust for very short heights (fallback to BMI 21.7 which is middle of normal) if formulas go weird
if (height < 152.4) {
// Use BMI 18.5 – 24.9 as the guide for short stature where linear formulas fail
minIdeal = 18.5 * (heightInMeters * heightInMeters);
maxIdeal = 24.9 * (heightInMeters * heightInMeters);
}
// — Updates Results UI —
idealWeightDisplay.innerText = minIdeal.toFixed(1) + " – " + maxIdeal.toFixed(1) + " kg";
bmiDisplay.innerText = bmi.toFixed(1);
// Determine Status
var status = "";
var statusColor = "";
if (bmi < 18.5) { status = "Underweight"; statusColor = "#dc3545"; }
else if (bmi < 25) { status = "Normal"; statusColor = "#28a745"; }
else if (bmi 0 ? "+" : "";
diffDisplay.innerText = diffSign + diff.toFixed(1) + " kg";
diffDisplay.style.color = Math.abs(diff) < 5 ? "#28a745" : "#666";
// Update Table
updateTable(devine, robinson, miller, hamwi, height);
// Update Chart
drawChart(bmi, heightInMeters, weight);
}
function updateTable(devine, robinson, miller, hamwi, height) {
var html = "";
// Helper to format row
function createRow(name, val, desc) {
return "
" + name + "
" + val.toFixed(1) + " kg
" + desc + "
";
}
if (height >= 150) {
html += createRow("Devine Formula", devine, "Most widely used for medical dosages.");
html += createRow("Robinson Formula", robinson, "Often used for slightly larger frames.");
html += createRow("Miller Formula", miller, "Based on anthropometric data from 1983.");
html += createRow("Hamwi Formula", hamwi, "Quick rule of thumb used in dietetics.");
} else {
html += "
Standard linear formulas (Devine, Robinson) are less accurate under 150cm. We recommend using the BMI range (18.5-24.9) calculated above.
";
}
tableBody.innerHTML = html;
}
function drawChart(currentBMI, heightInMeters, currentWeight) {
// Setup Canvas
var width = chartCanvas.offsetWidth;
var height = chartCanvas.offsetHeight;
chartCanvas.width = width;
chartCanvas.height = height;
// Clear
ctx.clearRect(0, 0, width, height);
// Define BMI Zones based on weight for this height
// Weight = BMI * h^2
var w18_5 = 18.5 * heightInMeters * heightInMeters; // End of Underweight
var w25_0 = 25.0 * heightInMeters * heightInMeters; // End of Normal
var w30_0 = 30.0 * heightInMeters * heightInMeters; // End of Overweight
// We need a max scale. Let's say up to BMI 40 or Current Weight + 20%
var maxWeight = Math.max(w30_0 * 1.2, currentWeight * 1.1);
// Drawing params
var barHeight = 60;
var barY = height / 2 – barHeight / 2;
var leftPad = 20;
var rightPad = 20;
var chartWidth = width – leftPad – rightPad;
// Scale conversion function
function getX(kg) {
return leftPad + (kg / maxWeight) * chartWidth;
}
// 1. Draw Zones
// Underweight (0 to 18.5)
ctx.fillStyle = "#add8e6"; // Light Blue
ctx.fillRect(leftPad, barY, getX(w18_5) – leftPad, barHeight);
// Normal (18.5 to 25)
ctx.fillStyle = "#28a745"; // Green
ctx.fillRect(getX(w18_5), barY, getX(w25_0) – getX(w18_5), barHeight);
// Overweight (25 to 30)
ctx.fillStyle = "#ffc107"; // Yellow
ctx.fillRect(getX(w25_0), barY, getX(w30_0) – getX(w25_0), barHeight);
// Obese (30+)
ctx.fillStyle = "#dc3545"; // Red
ctx.fillRect(getX(w30_0), barY, width – rightPad – getX(w30_0), barHeight);
// 2. Draw Labels for Zones
ctx.fillStyle = "#555";
ctx.font = "12px Arial";
ctx.textAlign = "center";
// Position labels roughly in center of zones
ctx.fillText("Under", (leftPad + getX(w18_5)) / 2, barY + barHeight + 20);
ctx.fillText("Healthy", (getX(w18_5) + getX(w25_0)) / 2, barY + barHeight + 20);
ctx.fillText("Over", (getX(w25_0) + getX(w30_0)) / 2, barY + barHeight + 20);
// 3. Draw Current Weight Marker
var currentX = getX(currentWeight);
// Clamp marker to chart area
if (currentX > width – rightPad) currentX = width – rightPad;
if (currentX < leftPad) currentX = leftPad;
ctx.fillStyle = "#004a99";
ctx.beginPath();
ctx.moveTo(currentX, barY – 10);
ctx.lineTo(currentX – 10, barY – 25);
ctx.lineTo(currentX + 10, barY – 25);
ctx.fill();
ctx.fillStyle = "#004a99";
ctx.font = "bold 14px Arial";
ctx.textAlign = "center";
ctx.fillText("You (" + currentWeight + "kg)", currentX, barY – 30);
// 4. Draw Legend/Title inside canvas (optional but nice)
ctx.textAlign = "left";
ctx.font = "12px Arial";
ctx.fillStyle = "#888";
ctx.fillText("Weight Distribution Scale (kg)", leftPad, height – 10);
}
function copyResults() {
var ideal = document.getElementById('idealWeightResult').innerText;
var bmi = document.getElementById('bmiResult').innerText;
var status = document.getElementById('statusResult').innerText;
var text = "Weight Calculator Results:\n" +
"Height: " + heightInput.value + " cm\n" +
"Current Weight: " + weightInput.value + " kg\n" +
"Ideal Weight Range: " + ideal + "\n" +
"BMI: " + bmi + " (" + status + ")";
// Create temporary textarea to copy
var el = document.createElement('textarea');
el.value = text;
document.body.appendChild(el);
el.select();
document.execCommand('copy');
document.body.removeChild(el);
// Visual feedback
var btn = document.querySelector('.btn-primary');
var originalText = btn.innerText;
btn.innerText = "Copied!";
setTimeout(function() {
btn.innerText = originalText;
}, 1500);
}
function resetCalculator() {
heightInput.value = 175;
weightInput.value = 70;
ageInput.value = 30;
genderInput.value = "male";
calculateWeight();
}
// Resize chart on window resize
window.onresize = function() {
calculateWeight();
};