How BMI is calculated
BMI = weight (kg) ÷ height (m)². In pounds and inches, multiply by 703: BMI = 703 × weight (lb) ÷ height (in)². A person who is 1.70 m and 72 kg has a BMI of 72 ÷ 2.89 = 24.9.
| BMI | Category (adults, WHO) |
|---|---|
| Under 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25 to 29.9 | Overweight |
| 30 to 34.9 | Obesity, class 1 |
| 35 to 39.9 | Obesity, class 2 |
| 40 or more | Obesity, class 3 |
Healthy weight by height
| Height | Healthy weight range (BMI 18.5 to 24.9) |
|---|---|
| 1.55 m (5 ft 1) | 44 to 60 kg (98 to 132 lb) |
| 1.60 m (5 ft 3) | 47 to 64 kg (104 to 140 lb) |
| 1.65 m (5 ft 5) | 50 to 68 kg (111 to 149 lb) |
| 1.70 m (5 ft 7) | 53 to 72 kg (118 to 159 lb) |
| 1.75 m (5 ft 9) | 57 to 76 kg (125 to 168 lb) |
| 1.80 m (5 ft 11) | 60 to 81 kg (132 to 178 lb) |
| 1.85 m (6 ft 1) | 63 to 85 kg (140 to 188 lb) |
What BMI does not tell you
- Muscle weighs too: athletes can have a high BMI with little fat.
- Where fat sits matters: belly fat carries more health risk. A waist under half your height is a good second check.
- Age and origin change the picture: some health bodies use lower cut-offs (for example 23 and 27.5) for people of Asian descent.
- It is for adults: children and teens use age and sex percentiles instead.
For a closer look at body composition, try the body fat calculator. To see a target weight in more ways, open the ideal weight calculator.
If your BMI is above 25
Losing even 5 to 10% of your weight improves blood pressure, blood sugar and cholesterol for most people. The calm way there is a small daily calorie deficit you can keep: see the date you could reach with the weight loss calculator, and the basics in our weight loss guide.
Questions about BMI
What is a healthy BMI?
For adults, a BMI from 18.5 to 24.9 is considered a healthy weight by the World Health Organization. 25 to 29.9 is overweight and 30 or more is obesity.
Is BMI accurate?
It is a quick, useful screen for groups of people, but it does not measure fat directly. Muscular people can score high, and it misses where fat is stored. Waist size and body fat estimates help complete the picture.
Is BMI different for women and men?
The formula and the adult categories are the same for women and men. Women tend to carry more fat at the same BMI, which BMI does not show.
How do I lower my BMI?
By losing weight, usually with a small calorie deficit kept over months, enough protein and regular movement. A drop of one BMI point is about 3 kg for someone 1.70 m tall.
Sources
- World Health Organization. A healthy lifestyle: WHO recommendations (body mass index).
- WHO Expert Consultation. Appropriate body-mass index for Asian populations. The Lancet, 2004.
- Centers for Disease Control and Prevention. Adult BMI categories.
This calculator gives general information, not medical advice. BMI is not suited to pregnancy, children or people with high muscle mass. Talk to your doctor about your own healthy weight.