BMI Calculator.
Know your number.
Calculate your Body Mass Index instantly. See your category, healthy weight range, and what it means. Free — no signup.
<18.5 Healthy
18.5–24.9 Overweight
25–29.9 Obese
30+
Calculate your exact calorie deficit and macro targets to reach your goal weight.
Try the Calorie Deficit Calculator →BMI categories explained
| BMI Range | Category | Health risk |
|---|---|---|
| Below 18.5 | Underweight | Increased risk of malnutrition |
| 18.5 – 24.9 | Healthy weight | Lowest health risk |
| 25.0 – 29.9 | Overweight | Moderate increased risk |
| 30.0 – 34.9 | Obese (Class I) | High risk |
| 35.0 – 39.9 | Obese (Class II) | Very high risk |
| 40.0+ | Obese (Class III) | Extremely high risk |
How is BMI calculated?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by the square of your height in metres: BMI = kg ÷ m².
For imperial units: BMI = (weight in lbs × 703) ÷ (height in inches)².
For example: a person who is 175cm tall and weighs 75kg has a BMI of 75 ÷ (1.75)² = 24.5 — in the healthy range.
Is BMI accurate?
BMI is a useful and widely-used screening tool, but it has limitations. It does not account for muscle mass, bone density, age, sex, or where fat is distributed on the body. Athletes with high muscle mass may have a high BMI despite being very healthy. Older adults may have a normal BMI but carry excess body fat.
Use BMI as a starting point alongside other measures like waist circumference, body fat percentage, and advice from a healthcare provider.
Frequently asked questions
What is a healthy BMI for women?
The healthy BMI range of 18.5–24.9 applies to adult women and men. However, research suggests women tend to carry more body fat than men at the same BMI, so some guidelines use slightly different thresholds by sex.
Does BMI change with age?
The standard BMI scale is designed for adults aged 18–65. For children and teenagers, BMI is assessed differently using age and sex-specific percentile charts. For older adults, a slightly higher BMI (around 25–27) may be associated with better outcomes.
What should I do if my BMI is too high?
A BMI above 25 suggests carrying excess weight. The most effective approach is a moderate calorie deficit combined with regular physical activity. Use our Calorie Deficit Calculator to find your daily target.