BMI Calculator
Body Mass Index from your height and weight, plus your healthy weight range. Metric or imperial — pick whichever feels natural.
Results
Your BMI
0.0
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Healthy range
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Difference
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How BMI is calculated
BMI compares your weight to your height squared. It's a quick screening tool — not a diagnosis. A muscular athlete and a sedentary person can have the same BMI but very different body compositions, so always read the number alongside other measures (waist circumference, body fat %, blood markers).
The formula
Imperial: BMI = (weight (lb) / height (in)2) × 703
WHO categories
- < 18.5 — Underweight
- 18.5 – 24.9 — Healthy weight
- 25.0 – 29.9 — Overweight
- 30.0 – 34.9 — Obese class I
- 35.0 – 39.9 — Obese class II
- ≥ 40.0 — Obese class III
Frequently asked questions
Is BMI accurate for athletes?
Not really. BMI doesn't distinguish muscle from fat, so well-trained athletes often land in "overweight" or even "obese" categories despite low body fat. Body fat percentage or waist-to-hip ratio is a better gauge for muscular builds.
Does BMI work for children?
For children and teens (ages 2–19), BMI is interpreted using age- and sex-specific percentiles, not the adult cutoffs above. This calculator uses the adult WHO ranges.
What if my BMI is just barely over 25?
The category boundaries are statistical conveniences, not physiological cliffs. The health risks change gradually, not at a single decimal. A BMI of 25.1 isn't meaningfully different from 24.9.