BMI Calculator
Enter your height and weight to get your body mass index, the adult category it falls in and the healthy weight range for your height.
Quick answer
BMI = weight (kg) ÷ height (m)². For adults, 18.5–24.9 is the healthy range, 25–29.9 overweight and 30+ obesity. BMI can't tell muscle from fat — check the body fat calculator too.
- Free
- No sign-up
- Fitness
- Updated October 2026
Your BMI
24.4
Healthy weight
- Category (adult WHO ranges)
- Healthy weight
- Healthy weight for your heightBMI 18.5–24.9
- 128.9 lb – 173.5 lb
Show the working
- Weight 77.11 kg, height 1.778 m
- BMI = 77.11 ÷ 1.778² = 24.4
About the BMI calculator
Body mass index compares your weight to your height. It is a quick screening number used by doctors and public-health bodies, not a diagnosis: it cannot tell muscle from fat, so very muscular people often score as “overweight” while being lean.
The categories used here are the World Health Organization adult ranges. They do not apply to children and teenagers, whose BMI is judged against age- and sex-specific percentiles, and some health bodies use lower cut-offs for people of Asian descent.
How to use it
- Choose US or metric units.
- Enter your weight.
- Enter your height in feet and inches, or centimetres.
- Read your BMI, its category and the weight range that gives a BMI of 18.5–24.9 at your height.
The formula
BMI = weight (kg) ÷ height (m)²
- In US units: BMI = 703 × weight (lb) ÷ height (in)².
- Under 18.5 underweight · 18.5–24.9 healthy · 25–29.9 overweight · 30 and above obesity.
Worked example
170 lb at 5 ft 10 in
- 170 lb = 77.1 kg; 70 in = 1.778 m.
- 1.778² = 3.161.
- 77.1 ÷ 3.161 = 24.4 → healthy weight range.
Frequently asked questions
Is BMI accurate for athletes?
Not very. BMI only uses height and weight, so muscle counts the same as fat. A body fat estimate or waist measurement says more for muscular people.
Does BMI work for children?
No. Under-18s are assessed with BMI-for-age percentile charts, because healthy body composition changes as children grow.
What is a healthy BMI?
For most adults, 18.5 to 24.9. Your doctor may use a different target depending on age, ethnicity and health history.
Results are estimates for healthy adults, not medical advice. Talk to a doctor or registered dietitian before major changes to diet or training, especially if you are pregnant or have a health condition.
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