Bmi Calculator for Amputees

Amputee BMI Calculator

Calculation Results

Estimated Theoretical Weight: kg

Adjusted BMI:

Category:

Note: This calculation uses the Amputee BMI adjustment formula to estimate your BMI as if the limb were still present.

function calculateAmputeeBMI() { var currentWeight = parseFloat(document.getElementById('calcWeight').value); var heightCm = parseFloat(document.getElementById('calcHeight').value); var checkboxes = document.getElementsByClassName('limb-check'); var totalPercentage = 0; if (isNaN(currentWeight) || isNaN(heightCm) || currentWeight <= 0 || heightCm <= 0) { alert('Please enter valid positive numbers for weight and height.'); return; } for (var i = 0; i = 100) { alert('Total limb percentage cannot be 100% or greater.'); return; } // Formula: Estimated Theoretical Weight = Current Weight / (1 – (Percentage / 100)) var theoreticalWeight = currentWeight / (1 – (totalPercentage / 100)); // Standard BMI Formula = Weight (kg) / (Height (m) ^ 2) var heightMeters = heightCm / 100; var bmi = theoreticalWeight / (heightMeters * heightMeters); var category = ""; var color = ""; if (bmi = 18.5 && bmi = 25 && bmi < 29.9) { category = "Overweight"; color = "#f0ad4e"; } else { category = "Obesity"; color = "#d9534f"; } document.getElementById('theoreticalWeight').innerText = theoreticalWeight.toFixed(2); document.getElementById('finalBMI').innerText = bmi.toFixed(2); document.getElementById('finalBMI').style.color = color; document.getElementById('bmiCategory').innerText = category; document.getElementById('bmiCategory').style.color = color; document.getElementById('bmiResultContainer').style.display = 'block'; }

Why Standard BMI Fails for Amputees

Body Mass Index (BMI) is a standard screening tool used to categorize weight and assess health risks. However, the standard formula—calculated by dividing weight by height squared—is inherently flawed for individuals with limb loss. Because a significant portion of body mass (the limb) is missing, a standard BMI calculation will result in an artificially low number, often incorrectly categorizing someone as "underweight" or "healthy" when their proportional body fat may indicate otherwise.

The Amputee BMI Adjustment Formula

To get an accurate health assessment, healthcare professionals use an "Estimated Theoretical Weight." This formula compensates for the missing mass based on standard anatomical weight distributions. The formula used by this calculator is:

Estimated Weight = Current Weight / (1 – % Amputation)

Once the theoretical weight is established, the standard BMI formula is applied to that adjusted weight to provide a more clinically relevant result.

Standard Limb Weight Percentages

Researchers have identified the average percentage of total body weight contributed by various limbs. These percentages are the foundation for clinical weight adjustment:

• Entire Arm: 5.0%
• Upper Arm: 2.7%
• Forearm: 1.6%
• Hand: 0.7%
• Entire Leg: 16.0%
• Above Knee (Thigh): 10.1%
• Below Knee (Lower Leg): 5.9%
• Foot: 1.5%

Calculation Example

Consider an individual who currently weighs 70 kg and stands 175 cm tall, with a below-the-knee amputation (5.9% of body weight).

1. Determine missing percentage: 5.9% (or 0.059 as a decimal).
2. Calculate Theoretical Weight: 70 / (1 – 0.059) = 70 / 0.941 = 74.39 kg.
3. Calculate BMI: 74.39 / (1.75 * 1.75) = 24.29.

Without the adjustment, the BMI would have been 22.86. While both fall in the normal range in this specific case, for individuals near the threshold of overweight or obesity categories, this adjustment is critical for accurate medical monitoring and nutritional planning.

Disclaimer: This calculator is for educational purposes only. It should not replace professional medical advice. Individuals with limb loss should work with dietitians or physicians familiar with amputee health to develop personalized health goals.