Amputee BMI Calculator
Accurate Body Mass Index adjustment for limb loss
Select Missing Limbs / Amputations:
Understanding BMI for Amputees
Body Mass Index (BMI) is a standard calculation based on a person's weight and height. However, for individuals with limb loss, the standard BMI formula is often inaccurate. Because a portion of the body's mass is missing, the raw weight of an amputee will result in an artificially low BMI that does not accurately reflect their actual body composition or health risks.
The Adjusted BMI Formula
To determine an accurate BMI for an amputee, we must first calculate the "Estimated Total Body Weight" as if the limb were still present. The formula used by this calculator is:
Adjusted Weight = Current Weight / (1.0 – Total % of missing limb)
Once the adjusted weight is determined, we use the standard BMI formula:
BMI = Adjusted Weight (kg) / [Height (m)]²
Standard Limb Weight Percentages
Medical research has established average percentages that specific limbs contribute to total body weight:
- Hand: 0.7%
- Forearm: 1.6%
- Upper Arm: 2.7%
- Entire Arm: 5.0%
- Foot: 1.5%
- Lower Leg (Below Knee): 5.9%
- Thigh: 10.1%
- Entire Leg (Above Knee): 16.0%
Example Calculation
Consider an individual who weighs 75 kg, is 180 cm tall, and has a transtibial (Below Knee) amputation.
- Identify missing percentage: Lower Leg = 5.9% (0.059).
- Calculate Adjusted Weight: 75 / (1 – 0.059) = 75 / 0.941 = 79.7 kg.
- Calculate BMI: 79.7 / (1.8 * 1.8) = 24.6.
Without adjustment, their BMI would have been 23.1. The adjustment provides a more accurate clinical picture for healthcare providers.