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Both calculators run independently — change the inputs on either side to compare results.

Health

BMI Calculator

Body Mass Index (BMI) is the most widely used screening tool for relating a person's weight to their height. It produces a single number that places adults into broad weight categories — underweight, healthy weight, overweight, or obese — and is used by the WHO, the CDC, and the NHS as a first-pass indicator of weight-related health risk. Enter your weight in kilograms and height in centimetres and the calculator returns your BMI in kg/m². The result is meant as a starting point for a conversation with a clinician, not a diagnosis on its own.

Underweight<18.5Normal18.5–25Overweight25–30Obese I30–35Obese II+35+
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Fitness

Body Fat Percentage Calculator

Estimate your body fat percentage from a tape measure using the US Navy circumference method — the same protocol the US military uses for fitness compliance. Enter your waist, neck, height (and hip if female) and the calculator returns body fat percentage, accurate to within ±3–4 percentage points compared to a DEXA scan.

Fill in the required fields to see your result.

Key differences

BMI CalculatorBody Fat Percentage Calculator
CategoryHealthFitness
Inputs required25
ResultYour BMIBody Fat Percentage (%)
What it doesBody Mass Index (BMI) is the most widely used screening tool for relating a person's weight to their height. It produces a single number that places adults into broad weight categories — underweight, healthy weight, overweight, or obese — and is used by the WHO, the CDC, and the NHS as a first-pass indicator of weight-related health risk. Enter your weight in kilograms and height in centimetres and the calculator returns your BMI in kg/m². The result is meant as a starting point for a conversation with a clinician, not a diagnosis on its own.Estimate your body fat percentage from a tape measure using the US Navy circumference method — the same protocol the US military uses for fitness compliance. Enter your waist, neck, height (and hip if female) and the calculator returns body fat percentage, accurate to within ±3–4 percentage points compared to a DEXA scan.