Professional tool for Ideal Body Weight (IBW) analysis and BMI estimation
Male
Female
Biological sex affects body composition formulas.
Enter height in centimeters (e.g., 175).
Please enter a valid height (50-300 cm).
Used to calculate BMI and variance.
Please enter a valid weight (10-500 kg).
Estimated Ideal Weight (Devine)
70.0kg
Healthy Range (BMI 18.5-25)
56.7 – 76.6 kg
Your BMI Score
26.1
Difference from Ideal
+10.0 kg
Formula Used: The primary result uses the Devine (1974) formula, which is the standard medical benchmark for ideal body weight calculations.
Comparison of different medical weight formulas for your height.
Formula Method
Estimated Ideal Weight (kg)
Year Developed
Figure 1: Comparison of your current weight vs. calculated ideal weight thresholds.
What is a Weight Calculator in Kg?
A weight calculator in kg is a specialized health tool designed to estimate an individual's ideal body weight (IBW) using standard metric measurements. Unlike general scales that simply display mass, a comprehensive weight calculator in kg interprets that mass in the context of your height and gender to provide medically relevant benchmarks.
This tool is essential for anyone tracking fitness goals, managing weight loss, or monitoring health conditions in a metric-first environment. While body weight alone does not paint a complete picture of health, knowing your ideal weight range in kilograms provides a foundational baseline for setting realistic dietary and fitness targets.
Common misconceptions often equate "ideal weight" with a single magic number. In reality, healthy weight is a range. This calculator provides estimates based on four distinct, clinically validated formulas to give you a broader perspective rather than a restrictive target.
Weight Calculator in Kg Formulas and Mathematical Explanation
Calculating ideal body weight is not a matter of guessing; it relies on anthropometric formulas developed by medical researchers. The most common formulas prioritize height as the main variable, as it is the most stable predictor of lean body mass.
Below are the primary algorithms used by this calculator. Note that all formulas originally used Imperial units (inches) and have been adapted here for metric calculation.
1. The Devine Formula (1974)
Originally developed to calculate drug dosages, this is the most widely used standard.
Men: 50 kg + 2.3 kg per inch over 5 feet
Women: 45.5 kg + 2.3 kg per inch over 5 feet
2. The Robinson Formula (1983)
A refinement of the Devine formula based on updated population data.
Men: 52 kg + 1.9 kg per inch over 5 feet
Women: 49 kg + 1.7 kg per inch over 5 feet
Variable Reference Table
Variables used in Ideal Body Weight calculations
Variable
Meaning
Unit
Typical Range
Base Mass
Starting constant based on gender
kg
45.5 – 56.2 kg
Height Factor
Weight added per unit of height
kg/inch
1.36 – 2.7 kg
Threshold Height
Height above which mass is added
feet
Fixed at 5 ft (152.4 cm)
Practical Examples (Real-World Use Cases)
Example 1: Male Athlete Planning a Cut
Scenario: Mark is a 180 cm male currently weighing 90 kg. He wants to know his ideal baseline before factoring in muscle mass.
Input: Height: 180 cm, Gender: Male, Current: 90 kg.
Calculation: 180 cm is approx 5ft 11in. That is 11 inches over 5ft.
Devine Result: 50 + (2.3 × 11) = 75.3 kg.
Interpretation: Mark is roughly 14.7 kg over the "medical ideal." However, if he has high muscle density, a weight calculator in kg serves as a baseline, not a limit. He might target 80 kg instead of 75 kg.
Example 2: Female Health Monitoring
Scenario: Sarah is 165 cm tall and weighs 55 kg. She wants to ensure she isn't underweight.
Input: Height: 165 cm, Gender: Female.
Calculation: 165 cm is approx 5ft 5in. That is 5 inches over 5ft.
Robinson Result: 49 + (1.7 × 5) = 57.5 kg.
BMI Range: 18.5 to 25 BMI for 165 cm is roughly 50.4 kg to 68 kg.
Interpretation: At 55 kg, Sarah is slightly below the specific Robinson target of 57.5 kg but well within the healthy BMI range. No intervention is needed based on this metric alone.
How to Use This Weight Calculator in Kg
Select Gender: Choose Male or Female. This adjusts the base constant in the formulas (men typically start with a higher base lean mass).
Enter Height: Input your height in centimeters (cm). If you know your height in meters (e.g., 1.75m), multiply by 100 (175 cm).
Enter Current Weight: Input your weight in kilograms. This allows the tool to calculate your current BMI and the difference from your ideal weight.
Review Results:
Look at the Primary Result for the standard Devine estimate.
Check the Healthy Range to see the wider acceptable window (BMI 18.5–25).
Use the chart to visualize where you stand relative to the calculated ideal.
Key Factors That Affect Weight Calculator Results
While a weight calculator in kg provides mathematically sound estimates, biological reality is complex. Several financial and physical factors influence how these numbers should be interpreted:
Muscle Mass vs. Fat: Muscle is denser than fat. An athlete may weigh significantly more than their "ideal weight" but have a low body fat percentage and excellent health.
Bone Frame Size: The formulas above assume a medium frame. Users with larger skeletal frames (wrist circumference > 7 inches for men) may physiologically need to weigh 10% more than the calculated value.
Age and Metabolism: As we age, metabolic rate often slows, and muscle mass may decrease. Sarcopenia (muscle loss) in older adults might make a lower weight less healthy than a slightly higher weight preserved as muscle.
Hydration Levels: Daily weight can fluctuate by 1-2 kg due to water retention, salt intake, or glycogen storage. Never rely on a single weigh-in.
Health History: Individuals recovering from illness or with specific chronic conditions may have different target weight ranges prescribed by doctors.
Pregnancy: These calculators are not applicable for pregnant women, where weight gain is a necessary and healthy physiological process.
Frequently Asked Questions (FAQ)
1. Why does the calculator give different results for different formulas?
Different formulas were developed in different decades using different population datasets. The Devine formula is the most common for medical dosing, while the Robinson formula attempted to correct for modern body types. It is best to view them as a range rather than conflicting truths.
2. Is BMI or Ideal Body Weight more accurate?
BMI is a general screening tool for populations, while Ideal Body Weight (IBW) formulas are more specific to linear height-weight ratios. Neither measures body fat percentage directly. For a complete picture, consider a DEXA scan or caliper test.
3. Can I use this weight calculator in kg for children?
No. Children and adolescents are still growing, and their height-weight ratios change rapidly. Use a pediatric growth chart percentile calculator instead.
4. What if I am very short or very tall?
Standard IBW formulas are most accurate for heights between 150 cm and 190 cm. For extremely tall or short individuals, BMI ranges tend to be more reliable than linear equations like Devine or Hamwi.
5. How do I convert pounds to kilograms?
To convert lbs to kg, divide the pound value by 2.20462. For example, 150 lbs / 2.20462 = 68.03 kg.
6. What is a healthy BMI range?
According to the WHO, a healthy BMI for adults is generally between 18.5 and 24.9. A BMI below 18.5 is considered underweight, while 25.0 to 29.9 is classified as overweight.
7. Does muscle weigh more than fat?
Technically, a kilogram of muscle weighs the same as a kilogram of fat. However, muscle is much more compact. One liter of muscle weighs roughly 1.06 kg, while one liter of fat weighs roughly 0.9 kg.
8. How often should I check my weight?
Weekly weigh-ins are generally better than daily ones to avoid obsessing over normal hydration fluctuations. Weigh yourself at the same time of day, ideally in the morning, for consistency.
Related Tools and Internal Resources
Enhance your health tracking with these related calculators and guides:
// Global State
var ctx = null; // Canvas context
var chartInstance = null; // We are building a custom chart, but this holds state
// Initialize
window.onload = function() {
calculateWeight();
};
function calculateWeight() {
// 1. Get Inputs
var gender = document.getElementById('gender').value;
var height = parseFloat(document.getElementById('height').value);
var currentWeight = parseFloat(document.getElementById('currentWeight').value);
// 2. Validate
var heightError = document.getElementById('heightError');
var weightError = document.getElementById('weightError');
var isValid = true;
if (isNaN(height) || height 300) {
heightError.style.display = 'block';
isValid = false;
} else {
heightError.style.display = 'none';
}
if (isNaN(currentWeight) || currentWeight 500) {
weightError.style.display = 'block';
isValid = false;
} else {
weightError.style.display = 'none';
}
if (!isValid) return;
// 3. Calculation Logic
// Convert Height to Inches for Formulas (Standard formulas use inches)
// 1 inch = 2.54 cm
var heightInInches = height / 2.54;
var inchesOver5Ft = heightInInches – 60;
// Ensure non-negative (though UI min is 50cm which is < 5ft, formulas break below 5ft usually)
// For logic sake, if < 5ft, we just assume base weight minus the factor?
// Standard medical practice usually stops these formulas at 5ft.
// We will clamp inchesOver5Ft to 0 for the "base" logic or allow negative subtraction if logic holds.
// Actually, for 0 ? "+" + diff.toFixed(1) : diff.toFixed(1);
document.getElementById('diffResult').innerText = diffText + " kg";
document.getElementById('diffResult').style.color = (bmi >= 18.5 && bmi <= 25) ? '#28a745' : '#dc3545';
// Update Table
var tbody = document.getElementById('formulaTableBody');
tbody.innerHTML = '';
var formulas = [
{ name: "Devine Formula", val: devine, year: "1974" },
{ name: "Robinson Formula", val: robinson, year: "1983" },
{ name: "Miller Formula", val: miller, year: "1983" },
{ name: "Hamwi Formula", val: hamwi, year: "1964" }
];
for (var i = 0; i < formulas.length; i++) {
var row = "
" +
"
" + formulas[i].name + "
" +
"
" + formulas[i].val.toFixed(1) + " kg
" +
"
" + formulas[i].year + "
" +
"
";
tbody.innerHTML += row;
}
// 5. Draw Chart
drawChart(currentWeight, devine, minHealthy, maxHealthy);
}
function drawChart(current, ideal, minH, maxH) {
var canvas = document.getElementById('weightChart');
if (!canvas.getContext) return;
var ctx = canvas.getContext('2d');
// Resize for retina/display
var rect = canvas.parentNode.getBoundingClientRect();
canvas.width = rect.width;
canvas.height = rect.height;
var width = canvas.width;
var height = canvas.height;
var padding = 50;
var chartHeight = height – (padding * 2);
var chartWidth = width – (padding * 2);
// Determine Scale
var maxValue = Math.max(current, maxH, ideal) * 1.2;
var minValue = 0;
ctx.clearRect(0, 0, width, height);
// Helper to map value to Y pos
function getY(val) {
return height – padding – ((val / maxValue) * chartHeight);
}
// Draw Axis
ctx.beginPath();
ctx.moveTo(padding, padding);
ctx.lineTo(padding, height – padding);
ctx.lineTo(width – padding, height – padding);
ctx.strokeStyle = '#333';
ctx.stroke();
// Bar Config
var barWidth = chartWidth / 4; // 3 bars roughly
var spacing = chartWidth / 4;
// 1. Min Healthy Bar
var x1 = padding + (spacing * 0.5) – (barWidth/2);
var y1 = getY(minHealthyLocal(minH)); // Helper wrapper
var h1 = (height – padding) – y1;
// Draw Healthy Range (Background area concept)
// Actually, let's draw 3 Bars: Lower Healthy, Ideal, Current
// Bar 1: Lower Healthy Limit
ctx.fillStyle = '#28a745';
ctx.fillRect(x1, getY(minH), barWidth, (height-padding) – getY(minH));
ctx.fillStyle = '#000';
ctx.textAlign = 'center';
ctx.fillText("Min Healthy", x1 + barWidth/2, height – padding + 20);
ctx.fillText(minH.toFixed(1), x1 + barWidth/2, getY(minH) – 10);
// Bar 2: Ideal (Devine)
var x2 = padding + (spacing * 1.5) – (barWidth/2);
ctx.fillStyle = '#004a99';
ctx.fillRect(x2, getY(ideal), barWidth, (height-padding) – getY(ideal));
ctx.fillStyle = '#000';
ctx.fillText("Ideal (Devine)", x2 + barWidth/2, height – padding + 20);
ctx.fillText(ideal.toFixed(1), x2 + barWidth/2, getY(ideal) – 10);
// Bar 3: Current
var x3 = padding + (spacing * 2.5) – (barWidth/2);
ctx.fillStyle = (current >= minH && current <= maxH) ? '#17a2b8' : '#dc3545'; // Teal if healthy, Red if not
ctx.fillRect(x3, getY(current), barWidth, (height-padding) – getY(current));
ctx.fillStyle = '#000';
ctx.fillText("Current", x3 + barWidth/2, height – padding + 20);
ctx.fillText(current.toFixed(1), x3 + barWidth/2, getY(current) – 10);
// Grid lines
ctx.strokeStyle = '#e0e0e0';
ctx.beginPath();
for (var j = 0; j <= 5; j++) {
var gridVal = (maxValue / 5) * j;
var gridY = getY(gridVal);
ctx.moveTo(padding, gridY);
ctx.lineTo(width – padding, gridY);
ctx.fillText(Math.round(gridVal), padding – 30, gridY + 5);
}
ctx.stroke();
}
function minHealthyLocal(val) {
return val; // pass through
}
function resetCalculator() {
document.getElementById('gender').value = 'male';
document.getElementById('height').value = '175';
document.getElementById('currentWeight').value = '80';
calculateWeight();
}
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"BMI Score: " + bmi + "\n" +
"Healthy Range: " + range + "\n" +
"Generated by Professional Weight Calculator.";
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