BMI Calculator
Enter your height and weight to instantly see your Body Mass Index (BMI) and which standard WHO weight category it falls into — switch between metric and imperial units at any time.
How it works
BMI is calculated by dividing your weight in kilograms by the square of your height in metres (BMI = weight ÷ height²). If you enter imperial units, they're converted to metric first so the same formula applies. The result places you into one of four standard World Health Organization weight categories.
Tip
BMI is a quick screening tool, not a diagnosis — it doesn't distinguish between muscle and fat, so athletes and very muscular people are often classified as "overweight" even at a healthy body-fat percentage.
Example
A person who is 1.75 m tall and weighs 70 kg has a BMI of 70 ÷ 1.75² ≈ 22.9, which falls in the "normal weight" range — useful context when a doctor, insurer or fitness app mentions your BMI without further explanation.
Frequently asked questions
- Is BMI a medical assessment?
- No — BMI is a general rule-of-thumb estimate based on population averages, and it doesn't account for age, sex, muscle mass, bone density or where fat is stored on the body. It's not a substitute for a proper medical assessment; if you have concerns about your weight or health, talk to a doctor or another qualified healthcare professional.
- What is a healthy BMI range?
- For most adults, the WHO defines 18.5–24.9 as the "normal weight" range, under 18.5 as underweight, 25–29.9 as overweight, and 30 or above as obese. These thresholds are population averages and are typically not applied the same way to children, teenagers, pregnant women or very elderly people.
- Is BMI calculated the same way for men and women?
- Yes — the formula itself (weight ÷ height²) and the WHO category thresholds are the same for adult men and women. What differs between people is how well BMI reflects actual body composition, since it cannot separate muscle from fat.
Further reading
More tools in this category
Due Date Calculator
Estimate your baby's due date and current week of pregnancy from your last period or conception date.
Calorie Calculator (TDEE)
Estimate your daily calorie needs — BMR and TDEE — from your age, height, weight and activity level.
Body Fat Calculator
Estimate your body fat percentage from neck, waist, and height measurements using the U.S. Navy method.
Sleep Cycle Calculator
Find the best time to go to bed or wake up, based on 90-minute sleep cycles.
Water Intake Calculator
Estimate how much water to drink each day based on your body weight, activity level and climate.
Macro Calculator
Split a daily calorie target into protein, carb and fat grams based on your diet goal.