.calc-section { margin-bottom: 20px; }
.calc-label { display: block; font-weight: 700; margin-bottom: 8px; color: #2c3e50; }
.calc-input { width: 100%; padding: 12px; border: 2px solid #ddd; border-radius: 6px; box-sizing: border-box; font-size: 16px; transition: border-color 0.3s; }
.calc-input:focus { border-color: #3498db; outline: none; }
.calc-select { width: 100%; padding: 12px; border: 2px solid #ddd; border-radius: 6px; background-color: #fff; font-size: 16px; }
.calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 15px; }
.btn-calculate { background-color: #27ae60; color: white; padding: 15px 25px; border: none; border-radius: 6px; cursor: pointer; font-size: 18px; font-weight: bold; width: 100%; margin-top: 10px; transition: background-color 0.3s; }
.btn-calculate:hover { background-color: #219150; }
#bmi-result-area { margin-top: 25px; padding: 20px; border-radius: 8px; background-color: #f8f9fa; border-left: 5px solid #27ae60; display: none; }
.result-value { font-size: 24px; font-weight: bold; color: #27ae60; }
.category-badge { display: inline-block; padding: 4px 12px; border-radius: 20px; font-size: 14px; font-weight: bold; margin-top: 5px; }
.checkbox-group { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 10px; }
.checkbox-item { display: flex; align-items: center; background: #f1f3f5; padding: 10px; border-radius: 6px; cursor: pointer; font-size: 14px; }
.checkbox-item input { margin-right: 10px; transform: scale(1.2); }
.unit-toggle { display: flex; margin-bottom: 20px; background: #eee; border-radius: 6px; padding: 4px; }
.unit-btn { flex: 1; padding: 8px; border: none; border-radius: 4px; cursor: pointer; background: transparent; transition: 0.3s; }
.unit-btn.active { background: #fff; box-shadow: 0 2px 4px rgba(0,0,0,0.1); font-weight: bold; }
@media (max-width: 600px) { .calc-grid, .checkbox-group { grid-template-columns: 1fr; } }
var currentUnit = 'metric';
function setUnits(unit) {
currentUnit = unit;
var metricBtn = document.getElementById('metric-btn');
var imperialBtn = document.getElementById('imperial-btn');
var labelWeight = document.getElementById('label-weight');
var labelHeight = document.getElementById('label-height');
if (unit === 'metric') {
metricBtn.classList.add('active');
imperialBtn.classList.remove('active');
labelWeight.innerText = 'Weight (kg)';
labelHeight.innerText = 'Height (cm)';
} else {
metricBtn.classList.remove('active');
imperialBtn.classList.add('active');
labelWeight.innerText = 'Weight (lbs)';
labelHeight.innerText = 'Height (inches)';
}
}
function calculateAmputeeBMI() {
var weight = parseFloat(document.getElementById('weight-input').value);
var height = parseFloat(document.getElementById('height-input').value);
var resultArea = document.getElementById('bmi-result-area');
var resultBmi = document.getElementById('result-bmi');
var resultCat = document.getElementById('result-category');
var resultTxt = document.getElementById('result-text');
var resultTheo = document.getElementById('theoretical-weight');
if (!weight || !height || weight <= 0 || height <= 0) {
alert("Please enter valid positive numbers for weight and height.");
return;
}
// Calculate total percentage of missing limbs
var checkboxes = document.getElementsByClassName('amp-check');
var totalMissingPercent = 0;
for (var i = 0; i < checkboxes.length; i++) {
if (checkboxes[i].checked) {
totalMissingPercent += parseFloat(checkboxes[i].value);
}
}
// Theoretical Weight calculation
// Formula: Actual Weight / (1 – decimal percent)
var multiplier = 1 – (totalMissingPercent / 100);
if (multiplier <= 0) {
alert("Invalid limb selection.");
return;
}
var theoreticalWeight = weight / multiplier;
var bmi = 0;
if (currentUnit === 'metric') {
// BMI = kg / m^2
var heightInMeters = height / 100;
bmi = theoreticalWeight / (heightInMeters * heightInMeters);
resultTheo.innerText = theoreticalWeight.toFixed(1) + " kg";
} else {
// BMI = (lbs * 703) / inches^2
bmi = (theoreticalWeight * 703) / (height * height);
resultTheo.innerText = theoreticalWeight.toFixed(1) + " lbs";
}
displayBMI(bmi);
}
function displayBMI(bmi) {
var resultArea = document.getElementById('bmi-result-area');
var resultBmi = document.getElementById('result-bmi');
var resultCat = document.getElementById('result-category');
var resultTxt = document.getElementById('result-text');
resultArea.style.display = 'block';
resultBmi.innerText = bmi.toFixed(1);
var category = "";
var color = "";
var description = "";
if (bmi = 18.5 && bmi = 25 && bmi < 30) {
category = "Overweight";
color = "#f39c12";
description = "Your adjusted BMI is in the overweight category. This may increase your risk for cardiovascular issues.";
} else {
category = "Obese";
color = "#e74c3c";
description = "Your adjusted BMI falls within the obesity range, which is associated with higher risks of diabetes and heart disease.";
}
resultCat.innerText = category;
resultCat.style.backgroundColor = color;
resultCat.style.color = "#fff";
resultTxt.innerText = description;
resultArea.scrollIntoView({ behavior: 'smooth' });
}
Amputee Adjusted BMI Calculator
Accurately calculate Body Mass Index for individuals with limb loss using the weight-compensation formula.
Your Results
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*Calculated based on an estimated theoretical body weight of —.
Why Use an Adjusted BMI for Amputees?
Standard BMI calculations can be misleading for individuals with limb loss. Body Mass Index is a ratio of weight to height; however, because a portion of the body's natural mass is missing, an amputee's actual scale weight is lower than what their height would normally support. This often leads to an artificially low BMI score that may mask overweight or obesity conditions.
The Calculation Methodology
This calculator utilizes the Amputee Weight Adjustment formula (often attributed to Osterkamp). To find the true BMI, we must first estimate what the person would weigh if they had all their limbs. This is called the "Theoretical Body Weight."
The formula used is:
Estimated Weight = Current Weight / (1 – % of Amputation)
Adjusted BMI = Estimated Weight / (Height)²
Adjusted BMI = Estimated Weight / (Height)²
Standard Weight Percentages
Health professionals typically use these percentages of total body weight for specific limbs:
- Hand: 0.7%
- Forearm: 1.6%
- Upper Arm: 2.7%
- Entire Arm: 5.0%
- Foot: 1.5%
- Lower Leg (BKA): 5.9%
- Thigh (AKA): 10.1%
- Entire Leg: 16.0%
Interpreting Your Results
Once the weight is adjusted, the standard World Health Organization (WHO) categories apply:
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal Weight |
| 25.0 – 29.9 | Overweight |
| 30.0 or Higher | Obesity |
Note: BMI is a screening tool and not a diagnostic of body fatness or overall health. Please consult with a healthcare professional or a registered dietitian for a comprehensive assessment.