BMI Calculator

Your BMI, your exact healthy weight range for your height, and a body fat percentage estimate — not just one number with no context.

✓ Free to use ✓ Metric & imperial ✓ Healthy weight range ✓ Body fat estimate

Units

Weight (kg)

Height (cm)

▸ Age & sex (for body fat estimate)

Age

Sex

Your BMI

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BMI Categories (WHO Standard)

BMI	Category
Under 18.5	Underweight
18.5 – 24.9	Healthy weight
25 – 29.9	Overweight
30 and above	Obese

What BMI actually measures — and its real limits

BMI is weight relative to height squared — a population-level screening tool, not an individual diagnosis. It can't distinguish muscle from fat, which is why a muscular athlete can show as "overweight" on BMI alone despite low body fat. It also doesn't account for fat distribution (visceral fat around organs carries more health risk than fat elsewhere at the same total weight), age, or sex differences in typical body composition. Use it as a starting signal, not a verdict.

How the body fat estimate works

This uses the Deurenberg formula: Body Fat % = (1.20 × BMI) + (0.23 × age) − (10.8 × sex) − 5.4, where sex = 1 for male and 0 for female. It's a population-average estimate accurate to within a few percentage points for most people — not a substitute for actual body composition measurement (DEXA scan, bioimpedance, or callipers) if you need precision.

BMI categories per the World Health Organization's standard adult classification. This calculator is for general information only — always consult a healthcare professional for a full individual assessment, especially for children, pregnant people, or elite athletes, where standard BMI categories don't apply well.

Frequently Asked Questions

Is BMI accurate for everyone?+

No — it's a useful screening tool but not a definitive health measure. It commonly overestimates body fat in muscular athletes and can underestimate it in older adults with low muscle mass. See exactly how it can misclassify athletes →

What is the healthiest BMI?+

A BMI between 20 and 22 is generally associated with the lowest health risks for most adults, though the "healthy" 18.5-24.9 range as a whole is considered low-risk, and optimal ranges do vary somewhat by age, sex and ethnicity.

Does BMI apply to children?+

No — children and teenagers need age- and sex-specific BMI percentile charts, not the fixed adult categories used here, because healthy body composition changes significantly through growth and puberty.