BMI Calculator
Work out your body mass index (BMI), see which weight category it falls into, and find the healthy weight range for your height. Metric and imperial units are both supported.
Adult thresholds (WHO). BMI does not distinguish muscle from fat.
Formula and calculation
Worked example
A person who weighs 70 kg and is 170 cm tall: height in meters is 1.70, so BMI = 70 ÷ (1.70 × 1.70) = 24.22. That falls in the normal-weight category (18.5–25), and the healthy weight range for 1.70 m is 53.5 – 72.3 kg.
What BMI does not tell you
BMI uses height and weight only, so it cannot distinguish muscle from fat. A muscular athlete can register as "overweight", and a person with low muscle mass can register as "normal" while carrying a high body-fat percentage. For a fuller picture, pair BMI with a waist measurement or body-fat estimate. BMI also uses fixed thresholds for all adults — if you are under 20, pregnant, or very tall or short, the numbers are a rough guide at best.
What the results mean
- BMI
- Body mass index — your weight in kilograms divided by the square of your height in meters. Adults are classified as underweight (below 18.5), normal weight (18.5–25), overweight (25–29.9) or obese (30 and above).
- Category
- The WHO weight category your BMI falls into, for adults 20 and over. The category boundaries are the same for men and women — BMI does not measure body composition.
- Healthy weight range
- The weight range that corresponds to a BMI of 18.5–25 at your height, in kilograms.
- Healthy weight range (imperial)
- The same healthy weight range expressed in pounds.
Frequently asked questions
Is BMI accurate for athletes and bodybuilders?
No. Muscle is denser than fat, so athletes commonly show BMIs in the overweight range despite very low body fat. Use body-fat percentage or waist circumference alongside BMI if you train regularly.
Does BMI work the same for men and women?
The categories use the same thresholds for both sexes. Women tend to carry more body fat than men at the same BMI, so at the same number a woman typically has a higher body-fat percentage — a known limitation of the measure.
Should children use this BMI calculator?
No — this calculator applies adult thresholds. Children and teens (2–19) need BMI-for-age percentiles from CDC or WHO growth charts, because body composition changes rapidly with growth.
What is a healthy BMI for my height?
The healthy range is a BMI of 18.5 to 25, which this calculator converts into a weight range for your height in both kilograms and pounds. Staying anywhere in that band is associated with the lowest risk in population studies.