Macros
BMI, BMR and TDEE are estimates from general formulas, not medical advice.
This BMI calculator works out your body mass index from height and weight in metric or imperial units and places it on the WHO adult chart. It also shows the healthy weight range for your height and your BMI Prime. Use it as a quick screening number for adults, not as a diagnosis.
How to use
- Choose metric (cm, kg) or imperial (ft, in, lb) units; your choice is remembered.
- Enter your height and weight. Your BMI, WHO category and healthy weight range appear below.
- On BMR, add your sex and age and pick a formula. Katch–McArdle also needs your body fat percentage.
- On TDEE, pick your activity level to see daily calories to maintain, lose or gain weight and a macro split in grams. Tap any result to copy it.
- These are estimates for healthy adults, not medical advice. Talk to a doctor or dietitian before major changes.
- BMI doesn’t tell fat from muscle: athletes may read as overweight, and older adults may have a normal BMI with little muscle. For children and teens under 20, use BMI-for-age percentiles instead.
- In studies, Mifflin–St Jeor (1990) usually comes closest for most adults. Harris–Benedict uses the 1984 revision. Katch–McArdle uses lean body mass and works best if you know your body fat.
- Calorie targets use about 7,700 kcal per kg (3,500 per lb) of body weight. Very low targets are flagged: most adults shouldn’t go below 1,200 (women) or 1,500 (men) kcal a day without supervision.
- Macros use 4 kcal per gram of protein and carbs and 9 kcal per gram of fat. Nothing you enter leaves your device or is stored.
How BMI is calculated
BMI = weight in kilograms ÷ height in meters squared, or 703 × pounds ÷ inches squared. Someone 1.75 m tall weighing 70 kg has a BMI of 70 ÷ 1.75² = 22.9. BMI Prime is BMI ÷ 25, so values above 1.0 are above the upper limit of the normal range.
For a height of 1.75 m, the WHO normal range of 18.5–24.9 corresponds to about 56.7–76.3 kg.
WHO categories and their limits
The World Health Organization classifies adult BMI as underweight below 18.5, normal 18.5–24.9, overweight (pre-obese) 25–29.9 and obese from 30, split into class I (30–34.9), II (35–39.9) and III (40 and above). Some Asian countries use lower cut-offs, such as 23 for overweight in Korea.
BMI does not distinguish fat from muscle or show where fat is stored, so athletes can read as overweight and older adults can look normal with little muscle. Children and teens need BMI-for-age percentiles. These are estimates from population formulas, not medical advice, and they are not meant for children, pregnancy or medical conditions. Nothing you enter leaves your device.
Frequently asked questions
How do I calculate my BMI?
Divide your weight in kilograms by your height in meters squared. 68 kg at 1.70 m gives 68 ÷ 2.89 = 23.5.
What is a healthy BMI?
For adults, the WHO normal range is 18.5 to 24.9. The calculator turns that into a weight range for your height.
Is BMI accurate for athletes?
Not very. Muscle is dense, so muscular people can have a BMI over 25 with little body fat. A waist measurement or body fat estimate adds context.
Is BMI different for men and women?
The formula and adult cut-offs are the same for both. Women on average carry more body fat at the same BMI.
Can children use this BMI calculator?
No. Under 20, BMI is interpreted with age- and sex-specific percentiles, such as the WHO or CDC growth charts.
What is BMI Prime?
Your BMI divided by 25, the upper limit of the normal range. A BMI Prime of 1.10 means 10% above that limit.