BMI Calculator
Calculate Body Mass Index and find your healthy weight range.
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How it works
Body Mass Index is your weight in kilograms divided by your height in meters squared. The calculator accepts metric (kg/cm) or imperial (lb/ft·in) and converts internally. Imperial pounds become kilograms by multiplying by 0.45359237; feet and inches become centimeters via 30.48 cm/ft and 2.54 cm/in. Categories follow the World Health Organization standard: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese. The tool also shows your healthy weight range (18.5 × h² to 24.9 × h²).
BMI = weight_kg / (height_m)²
// Healthy range:
// min = 18.5 × height_m²
// max = 24.9 × height_m²
Common use cases
- Tracking progress toward a healthy weight target alongside diet and exercise.
- Initial screening when starting a fitness program or health checkup.
- Comparing weight changes over time using a single normalized number.
See also: Age Calculator .
Frequently asked questions
Is BMI accurate for athletes?
No. Muscle is denser than fat, so muscular athletes (rugby players, bodybuilders) often score "overweight" or "obese" despite low body fat. BMI is a population-level screening tool, not a diagnosis. Body fat percentage or waist-to-height ratio is more meaningful for athletes.
Does BMI work for children?
Children use age- and sex-specific percentile charts, not the adult BMI categories shown here. For anyone under 18, consult the CDC or NHS pediatric BMI calculators instead.
What is the healthy weight range shown for?
It is the weight range that would put your BMI between 18.5 and 24.9 at your current height. Useful as a target band rather than a single goal weight.
Embed this tool
Add this free bmi calculator to your own website or blog — copy the code below and paste it into your page HTML. No signup, no API key.
<iframe src="https://otoolrun.com/embed/bmi-calculator/" width="100%" height="560" style="border:0;border-radius:12px" loading="lazy" title="BMI Calculator"></iframe>
<p style="font-size:14px"><a href="https://otoolrun.com/tools/bmi-calculator/">BMI Calculator by oToolRun</a></p>