Free Calculator
BMI Calculator
Work out your Body Mass Index from your height and weight, see which weight category you fall into, and find the healthy weight range for your height.
Your details
Your BMI
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Healthy weight for your height
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Where you sit
BMI is a general screening tool, not a diagnosis or medical advice. It cannot tell muscle from fat and does not account for age, sex or body composition. For a calorie and macro target, use the TDEE calculator.
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What is BMI?
BMI (Body Mass Index) is a simple number that compares your weight to your height. It is the most widely used quick check for whether an adult is a healthy weight, and it is what doctors, researchers and health services use as a first-pass screen. It does not measure body fat directly — it just uses your height and weight — but for most people it lines up reasonably well.
How BMI is calculated
- Metric: BMI = weight (kg) ÷ height (m)²
- Imperial: BMI = 703 × weight (lb) ÷ height (in)²
For example, someone who is 1.75 m tall and weighs 75 kg has a BMI of 75 ÷ (1.75 × 1.75) = 24.5, which sits in the healthy range.
BMI categories for adults
- Under 18.5 — underweight
- 18.5 to 24.9 — healthy weight
- 25 to 29.9 — overweight
- 30 and above — obese
The limits of BMI
BMI is handy but blunt. Because it only knows your height and weight, it can't distinguish muscle from fat — a lean, muscular athlete can score as "overweight" while carrying very little fat. It also ignores age, sex and where you store fat. Use it as one signal among several (waist measurement, how your clothes fit, energy levels), not as the final word on your health.
BMI tells you roughly where you stand today. If you want to change it, the lever is your calorie balance — that's where the TDEE calculator and tracking come in.
Frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). In imperial units it is 703 × weight in pounds ÷ height in inches squared. This calculator does the conversion for you whichever units you use.
What is a healthy BMI?
For most adults a BMI between 18.5 and 24.9 is classed as a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is in the obese range.
Is BMI accurate?
BMI is a useful, quick screening tool for populations, but it has real limitations for individuals. It only uses height and weight, so it cannot tell muscle from fat — very muscular people can read as "overweight" despite low body fat, and it does not account for age, sex, or where you carry fat. Treat it as a rough guide, not a diagnosis.
Does BMI tell me how many calories to eat?
No — BMI says nothing about calories. If you want a daily calorie and macro target, use our TDEE calculator instead, which estimates the calories you burn each day and turns that into goals for losing, maintaining or gaining weight.
Is BMI different for men and women?
The BMI formula and the standard adult categories are the same for men and women. On average women carry more body fat than men at the same BMI, which is one reason BMI is best used as a general guide alongside other measures like waist size.