Body Fat Estimator
Estimate body fat percentage from BMI with an age and gender adjustment. Enter BMI, age, and gender for a quick estimate. Health data never leaves your device — every calculation runs locally in your browser.
How to Use the Body Fat Estimator
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Calculate body fat percentage using the US Navy circumference method. Enter waist, neck, height, and hip measurements. Health data never leaves your device — every calculation runs locally in your browser.
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Frequently Asked Questions
How is body fat estimated from BMI?
The formula uses BMI, age, and gender to estimate body fat percentage: BF% = (1.20 × BMI) + (0.23 × Age) - (10.8 × Gender) - 5.4, where Gender = 1 for male, 0 for female.
How accurate is BMI-based estimation?
Typically within a few points of DEXA for average builds — an estimate for general fitness tracking, not a clinical measure. Less accurate for athletes with high muscle mass, elderly, or very lean individuals. Defaults (BMI 24, age 30, male) estimate 19.5%.
What fitness categories are shown?
Essential fat, athletes, fitness, acceptable, and obese ranges for both men and women. These follow WHO and ACSM guidelines.
What inputs do I need?
Your BMI, age, and gender — enter a BMI you already know or compute one first with the BMI calculator.
When using Body Fat Estimator, is my health data stored?
No. All calculations run locally in your browser. No health data is transmitted.
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Body Fat Percentage Calculator
Calculate body fat percentage using the US Navy circumference method. Enter waist, neck, height, and hip measurements. Health data never leaves your device — every calculation runs locally in your browser.
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Computes Body Mass Index from metric or imperial height and weight inputs, categorizing the result into underweight, normal, overweight, and obese, with a healthy weight range for your height. Health data never leaves your device — every calculation runs locally in your browser.
Last updated October 2026