Ideal Weight for Height and Age Calculator UK | Accurate Health Tool
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Estimated Ideal Weight
11st 5lbs
(72.1 kg)
Healthy BMI Range
60 – 81 kg
| Formula Method |
Calculated Weight (kg) |
Calculated Weight (st/lbs) |
Visual comparison of your ideal weight against BMI categories.
What is the Ideal Weight for Height and Age Calculator UK?
The ideal weight for height and age calculator uk is a specialized tool designed to help individuals determine a healthy body weight range based on established medical formulas. Unlike a simple scale reading, this calculator considers your biological sex, height, and body frame size to provide a personalized estimation. While "ideal weight" is a subjective term, medical professionals use these calculations to identify weight ranges associated with the lowest risk of health complications such as heart disease, diabetes, and hypertension.
This tool is particularly useful for UK residents as it offers results in both metric (kg) and imperial (stones and pounds) units, aligning with the measurements most commonly used in the British healthcare system (NHS). It is important to note that this calculator is intended for adults over the age of 18 and should be used as a guideline rather than a strict rule.
Ideal Weight Formulas and Mathematical Explanation
There is no single "perfect" formula for ideal weight. This calculator utilizes four of the most respected medical equations to provide a comprehensive average. Below is a breakdown of how these figures are derived.
1. Devine Formula (1974):
Male: 50kg + 2.3kg per inch over 5ft
Female: 45.5kg + 2.3kg per inch over 5ft
The Devine formula is the most widely used equation for calculating ideal body weight (IBW) in medical settings, particularly for dosing medications.
2. Robinson Formula (1983):
Male: 52kg + 1.9kg per inch over 5ft
Female: 49kg + 1.7kg per inch over 5ft
The Robinson formula was developed to refine the Devine equation, often providing slightly higher weight targets for men and lower for women.
Variables Table
| Variable |
Meaning |
Unit |
Typical Range |
| Height |
Vertical measurement of the body |
cm / ft & in |
140cm – 210cm |
| Base Weight |
Starting constant in formula |
kg |
45.5kg – 56.2kg |
| Increment |
Weight added per inch of height |
kg/inch |
1.36kg – 2.7kg |
Practical Examples (Real-World Use Cases)
Example 1: The Average UK Male
Profile: John is a 35-year-old male, 5ft 10in (178cm) tall with a medium frame.
- Input: Male, 35 years, 5ft 10in.
- Devine Calculation: 50kg + (2.3kg × 10 inches) = 73kg.
- Result: John's ideal weight is approximately 11st 7lbs (73kg).
- Interpretation: This weight places John squarely in the middle of the healthy BMI range, suggesting optimal metabolic health.
Example 2: The Petite Female
Profile: Sarah is a 28-year-old female, 5ft 2in (157cm) tall with a small frame.
- Input: Female, 28 years, 5ft 2in, Small Frame.
- Robinson Calculation: 49kg + (1.7kg × 2 inches) = 52.4kg.
- Frame Adjustment: Small frame reduces this by 10% → ~47.2kg.
- Result: Sarah's ideal weight is approximately 7st 6lbs (47kg).
- Interpretation: Without the frame adjustment, the standard formula might suggest a weight that is too heavy for her bone structure.
How to Use This Ideal Weight Calculator
- Select Your Gender: Biological sex affects body composition and the base constants used in the formulas.
- Enter Your Age: While the core formulas rely on height, age is used to validate that you are an adult (18+).
- Input Your Height: Choose between Imperial (Feet/Inches) or Metric (Centimetres). Accuracy here is crucial.
- Choose Frame Size: If you have smaller wrists and ankles, choose "Small". If you are broad-shouldered or have larger joints, choose "Large".
- Review Results: Look at the "Estimated Ideal Weight" for your target. Use the "Healthy BMI Range" to see the broader safe zone.
Key Factors That Affect Ideal Weight Results
While the ideal weight for height and age calculator uk provides a scientific estimate, several biological and lifestyle factors influence your true healthy weight.
- Muscle Mass: Muscle is denser than fat. An athlete may weigh more than the "ideal" calculation but have a low body fat percentage and be perfectly healthy.
- Bone Density: Frame size inputs help account for this, but individuals with naturally higher bone density will weigh more.
- Age: As we age, metabolism slows and muscle mass naturally decreases. Older adults (65+) often benefit from being slightly heavier (BMI 25-27) to provide a reserve against illness.
- Body Fat Distribution: Where you carry weight matters. Visceral fat (around the waist) is riskier than subcutaneous fat (hips/thighs).
- Hydration Levels: Daily weight can fluctuate by 1-2kg based on water retention and salt intake.
- Pregnancy: These formulas are not applicable to pregnant women, who have specific weight gain guidelines.
Frequently Asked Questions (FAQ)
1. Does age affect the ideal weight calculation?
Strictly speaking, the Devine and Robinson formulas rely on height. However, modern health guidelines suggest that ideal BMI ranges may shift slightly upwards as we age to protect against frailty.
2. Why is the result different from my BMI target?
BMI provides a wide range (e.g., 60kg to 80kg). The "Ideal Weight" formulas attempt to pinpoint a specific number within that range based on population averages.
3. Is this calculator accurate for bodybuilders?
No. High muscle mass will skew results. Bodybuilders should rely on body fat percentage measurements rather than standard weight tables.
4. What is the most accurate formula?
The Devine formula is the most widely accepted in the medical community, but the Robinson formula is often considered more accurate for modern populations.
5. How do I know my frame size?
A simple test is wrapping your thumb and middle finger around your wrist. If they overlap, you have a small frame. If they touch, medium. If they don't meet, large.
6. Can I use this for children?
No. Children and teenagers require specialized growth charts (centile charts) used by pediatricians.
7. Why are stones and pounds used?
This is an ideal weight for height and age calculator uk specific tool. While the NHS uses metric, the British public widely uses stones for personal weight tracking.
8. What if I am outside the ideal range?
Being outside the specific "ideal" number is normal. Focus on staying within the broader "Healthy BMI Range" displayed in the results section.
Related Tools and Internal Resources
// Global Variables
var ctx = document.getElementById('weightChart').getContext('2d');
var chartInstance = null;
// Initialization
window.onload = function() {
calculateWeight();
};
function toggleHeightInputs() {
var unit = document.querySelector('input[name="heightUnit"]:checked').value;
var imperialDiv = document.getElementById('imperialInputs');
var metricDiv = document.getElementById('metricInputs');
var feetInput = document.getElementById('feet');
var inchesInput = document.getElementById('inches');
var cmInput = document.getElementById('cm');
if (unit === 'imperial') {
imperialDiv.style.display = 'flex';
metricDiv.style.display = 'none';
// Convert CM to Ft/In for smooth UX
var cmVal = parseFloat(cmInput.value) || 0;
if (cmVal > 0) {
var totalInches = cmVal / 2.54;
feetInput.value = Math.floor(totalInches / 12);
inchesInput.value = Math.round(totalInches % 12);
}
} else {
imperialDiv.style.display = 'none';
metricDiv.style.display = 'block';
// Convert Ft/In to CM
var ftVal = parseFloat(feetInput.value) || 0;
var inVal = parseFloat(inchesInput.value) || 0;
if (ftVal > 0 || inVal > 0) {
var totalInches = (ftVal * 12) + inVal;
cmInput.value = Math.round(totalInches * 2.54);
}
}
calculateWeight();
}
function calculateWeight() {
// 1. Get Inputs
var gender = document.getElementById('gender').value;
var age = parseFloat(document.getElementById('age').value);
var frame = document.getElementById('frame').value;
var unit = document.querySelector('input[name="heightUnit"]:checked').value;
// 2. Validate & Normalize Height to Inches
var heightInches = 0;
var heightCm = 0;
if (unit === 'imperial') {
var ft = parseFloat(document.getElementById('feet').value) || 0;
var inc = parseFloat(document.getElementById('inches').value) || 0;
heightInches = (ft * 12) + inc;
heightCm = heightInches * 2.54;
} else {
heightCm = parseFloat(document.getElementById('cm').value) || 0;
heightInches = heightCm / 2.54;
}
// Validation Display
var ageError = document.getElementById('ageError');
var heightError = document.getElementById('heightError');
var isValid = true;
if (isNaN(age) || age 120) {
ageError.style.display = 'block';
isValid = false;
} else {
ageError.style.display = 'none';
}
if (heightInches 96) { // 3ft to 8ft reasonable range
heightError.style.display = 'block';
isValid = false;
} else {
heightError.style.display = 'none';
}
if (!isValid) return;
// 3. Calculate Formulas (Base is usually for 5ft, i.e., 60 inches)
var baseInches = heightInches – 60;
if (baseInches < 0) baseInches = 0; // Formulas don't work well below 5ft, clamp or handle
var devine = 0;
var robinson = 0;
var miller = 0;
var hamwi = 0;
if (gender === 'male') {
devine = 50 + (2.3 * baseInches);
robinson = 52 + (1.9 * baseInches);
miller = 56.2 + (1.41 * baseInches);
hamwi = 48 + (2.7 * baseInches);
} else {
devine = 45.5 + (2.3 * baseInches);
robinson = 49 + (1.7 * baseInches);
miller = 53.1 + (1.36 * baseInches);
hamwi = 45.5 + (2.2 * baseInches);
}
// Frame Size Adjustment (Applied to average or specific formulas, here applied to final average for simplicity or specific logic)
// Usually Frame size adjusts Hamwi by +/- 10%. Let's apply it to all for the "Estimated Ideal"
var frameMultiplier = 1.0;
if (frame === 'small') frameMultiplier = 0.9;
if (frame === 'large') frameMultiplier = 1.1;
// Apply frame adjustment
var avgWeight = ((devine + robinson + miller + hamwi) / 4) * frameMultiplier;
// BMI Range (18.5 – 24.9)
var heightM = heightCm / 100;
var minBMIWeight = 18.5 * (heightM * heightM);
var maxBMIWeight = 24.9 * (heightM * heightM);
// 4. Update UI
updateResultDisplay(avgWeight, minBMIWeight, maxBMIWeight, devine, robinson, miller, hamwi, frameMultiplier);
drawChart(minBMIWeight, maxBMIWeight, avgWeight);
}
function updateResultDisplay(avg, minBMI, maxBMI, devine, robinson, miller, hamwi, frameMult) {
// Main Result
document.getElementById('mainResultStones').innerText = kgToStones(avg);
document.getElementById('mainResultKg').innerText = "(" + avg.toFixed(1) + " kg)";
// Metrics
document.getElementById('bmiRange').innerText = minBMI.toFixed(1) + " – " + maxBMI.toFixed(1) + " kg";
document.getElementById('devineResult').innerText = (devine * frameMult).toFixed(1) + " kg";
document.getElementById('robinsonResult').innerText = (robinson * frameMult).toFixed(1) + " kg";
// Table
var tbody = document.getElementById('formulaTableBody');
tbody.innerHTML = "";
var formulas = [
{ name: "Devine (1974)", val: devine * frameMult },
{ name: "Robinson (1983)", val: robinson * frameMult },
{ name: "Miller (1983)", val: miller * frameMult },
{ name: "Hamwi (1964)", val: hamwi * frameMult }
];
for (var i = 0; i < formulas.length; i++) {
var row = "
";
row += "| " + formulas[i].name + " | ";
row += "" + formulas[i].val.toFixed(1) + " | ";
row += "" + kgToStones(formulas[i].val) + " | ";
row += "
";
tbody.innerHTML += row;
}
}
function kgToStones(kg) {
var totalLbs = kg * 2.20462;
var stones = Math.floor(totalLbs / 14);
var lbs = Math.round(totalLbs % 14);
return stones + "st " + lbs + "lbs";
}
function drawChart(minBMI, maxBMI, ideal) {
var canvas = document.getElementById('weightChart');
var ctx = canvas.getContext('2d');
// Clear
ctx.clearRect(0, 0, canvas.width, canvas.height);
// Dimensions
var w = canvas.width;
var h = canvas.height;
var padding = 20;
var barHeight = 40;
var barY = h / 2 – barHeight / 2;
// Scale: Show range from minBMI – 15kg to maxBMI + 15kg
var scaleMin = minBMI – 15;
var scaleMax = maxBMI + 15;
var range = scaleMax – scaleMin;
function getX(val) {
return padding + ((val – scaleMin) / range) * (w – (2 * padding));
}
// Draw Background Bar (Underweight / Overweight context)
ctx.fillStyle = "#e9ecef";
ctx.fillRect(padding, barY, w – 2 * padding, barHeight);
// Draw Healthy Range (Green)
var x1 = getX(minBMI);
var x2 = getX(maxBMI);
ctx.fillStyle = "rgba(40, 167, 69, 0.3)";
ctx.fillRect(x1, barY, x2 – x1, barHeight);
ctx.strokeStyle = "#28a745";
ctx.strokeRect(x1, barY, x2 – x1, barHeight);
// Label Healthy Range
ctx.fillStyle = "#28a745";
ctx.font = "12px Arial";
ctx.textAlign = "center";
ctx.fillText("Healthy BMI Range", x1 + (x2 – x1) / 2, barY – 10);
// Draw Ideal Marker
var xIdeal = getX(ideal);
ctx.beginPath();
ctx.moveTo(xIdeal, barY – 5);
ctx.lineTo(xIdeal, barY + barHeight + 5);
ctx.strokeStyle = "#004a99";
ctx.lineWidth = 3;
ctx.stroke();
// Label Ideal
ctx.fillStyle = "#004a99";
ctx.font = "bold 12px Arial";
ctx.fillText("Your Ideal", xIdeal, barY + barHeight + 20);
ctx.fillText(ideal.toFixed(1) + "kg", xIdeal, barY + barHeight + 35);
}
function resetCalculator() {
document.getElementById('age').value = 30;
document.getElementById('feet').value = 5;
document.getElementById('inches').value = 9;
document.getElementById('cm').value = 175;
document.getElementById('gender').value = 'male';
document.getElementById('frame').value = 'medium';
// Reset radio to imperial
var radios = document.getElementsByName('heightUnit');
for(var i=0; i<radios.length; i++) {
if(radios[i].value === 'imperial') radios[i].checked = true;
}
toggleHeightInputs();
calculateWeight();
}
function copyResults() {
var st = document.getElementById('mainResultStones').innerText;
var kg = document.getElementById('mainResultKg').innerText;
var bmi = document.getElementById('bmiRange').innerText;
var text = "Ideal Weight Calculation:\n";
text += "Estimated Ideal Weight: " + st + " " + kg + "\n";
text += "Healthy BMI Range: " + bmi + "\n";
text += "Generated by Ideal Weight Calculator UK";
var tempInput = document.createElement("textarea");
tempInput.value = text;
document.body.appendChild(tempInput);
tempInput.select();
document.execCommand("copy");
document.body.removeChild(tempInput);
var btn = document.querySelector('.btn-copy');
var originalText = btn.innerText;
btn.innerText = "Copied!";
setTimeout(function(){ btn.innerText = originalText; }, 2000);
}