Body Fat Percentage Calculator (BMI Method) Formula
Understand the math behind the body fat percentage calculator (bmi method). Each variable explained with a worked example.
Formulas Used
Estimated Body Fat %
body_fat_pct = 1.20 * bmi + 0.23 * age - 16.2BMI
bmi_display = bmiLean Mass %
lean_mass_pct = 100 - (1.20 * bmi + 0.23 * age - 16.2)Variables
| Variable | Description | Default |
|---|---|---|
weight_lbs | Weight(lbs) | 180 |
height_feet | Height (feet)(ft) | 5 |
height_inches | Height (inches)(in) | 10 |
age | Age(years) | 30 |
total_inches | Derived value= height_feet * 12 + height_inches | calculated |
bmi | Derived value= (weight_lbs * 703) / (total_inches * total_inches) | calculated |
How It Works
BMI-Based Body Fat Estimation (Male)
Body Fat % = 1.20 x BMI + 0.23 x Age - 16.2
This formula was developed by Deurenberg et al. and provides an estimate of body fat percentage using BMI and age.
Note: This is the male formula. The female formula uses different constants (1.20 x BMI + 0.23 x Age - 5.4).
Worked Example
A 30-year-old male, 180 lbs, 5'10".
weight_lbs = 180height_feet = 5height_inches = 10age = 30
- 01BMI = (180 x 703) / (70 x 70) = 25.8
- 02Body Fat = 1.20 x 25.8 + 0.23 x 30 - 16.2
- 03= 31.0 + 6.9 - 16.2 = 21.7%
Ready to run the numbers?
Open Body Fat Percentage Calculator (BMI Method)