Quick answer
BMI = weight in kg ÷ height in metres squared. Someone 1.70 m tall weighing 65 kg has a BMI of 22.5. On the WHO scale a healthy BMI is 18.5–24.9; on the Asian scale recommended for people of Asian origin it is 18.5–22.9, with overweight from 23 and obesity from 25.
What is BMI?
Body mass index is the quickest way to see whether an adult's weight is low, healthy or high for their height. This calculator gives your BMI, its category on both the international WHO scale and the lower Asian cut-offs, the healthy weight range for your height and how many kilograms you are above or below it. It accepts cm/kg or feet, inches and pounds.
How to work out your BMI
- 1
Choose cm and kg, or feet, inches and pounds.
- 2
Enter your height without shoes and your weight, ideally measured in the morning.
- 3
Pick the classification you want highlighted: WHO international or Asian cut-offs. Both are always shown.
- 4
Read your BMI, its position on the coloured bar, the healthy weight range and how far you are from it.
Adult BMI categories
| Category | WHO international | Asia-Pacific |
|---|---|---|
| Severe thinness | < 16 | < 16 |
| Moderate thinness | 16 – 16.9 | 16 – 16.9 |
| Mild thinness | 17 – 18.4 | 17 – 18.4 |
| Normal | 18.5 – 24.9 | 18.5 – 22.9 |
| Overweight | 25 – 29.9 (pre-obese) | 23 – 24.9 (at risk) |
| Obesity class I | 30 – 34.9 | 25 – 29.9 |
| Obesity class II | 35 – 39.9 | ≥ 30 |
| Obesity class III | ≥ 40 | Not separated |
Sources: WHO adult BMI classification; WHO Western Pacific Region, IASO and IOTF (2000), “The Asia-Pacific perspective: Redefining obesity and its treatment”.
Healthy weight by height (WHO, BMI 18.5–24.9)
| Height | Healthy weight | Overweight from |
|---|---|---|
| 155 cm (5 ft 1 in) | 44.4 – 59.8 kg | 60.1 kg |
| 165 cm (5 ft 5 in) | 50.4 – 67.8 kg | 68.1 kg |
| 175 cm (5 ft 9 in) | 56.7 – 76.3 kg | 76.6 kg |
| 185 cm (6 ft 1 in) | 63.3 – 85.2 kg | 85.6 kg |
Examples
Same person, two scales
165 cm and 64 kg gives a BMI of 23.5: normal on the WHO scale but overweight (at risk) on the Asian scale.
How much to lose
170 cm and 78 kg gives a BMI of 27.0. The Asian healthy range for that height is 53.5–66.2 kg, about 11.8 kg lower.
US units
5 ft 10 in and 170 lb (77.1 kg) gives a BMI of 24.4.
Common problems
- Using adult BMI for children.
- Under 20, use BMI-for-age charts from the WHO instead of these adult thresholds.
- Muscular people show as overweight.
- BMI can't tell muscle from fat. Combine it with waist circumference or body fat percentage.
- Height typed in metres.
- The metric field expects centimetres: type 170, not 1.7.
Why lower cut-offs for Asian populations?
At the same BMI, people of Asian origin tend to carry more body fat and develop type 2 diabetes and heart disease earlier. The WHO Western Pacific Region, IASO and IOTF therefore proposed lower thresholds: overweight from 23 and obesity from 25.
What BMI can't tell you
BMI is a screening tool, not a diagnosis. It says nothing about where fat is stored, and belly fat carries more risk than fat on the hips. A waist measurement adds useful information.
- Not for under-20s, pregnancy or breastfeeding.
- Older adults and athletes may need other measures.
- Talk to a doctor before changing weight if you have a health condition.
Glossary
- BMI
- Body mass index: weight in kilograms divided by the square of height in metres.
- Overweight
- BMI above the healthy range but below obesity: 25–29.9 (WHO) or 23–24.9 (Asian).
- Obesity
- Excess body fat that harms health: BMI 30+ (WHO) or 25+ (Asian).
Frequently asked questions
What is a healthy BMI?
18.5–24.9 on the WHO scale, 18.5–22.9 on the Asian scale.
How is BMI calculated?
Weight (kg) ÷ height (m)². For pounds and inches the tool converts for you.
Which scale should I use?
The Asian cut-offs are recommended for people of Asian origin; the WHO scale for everyone else. Both are shown.
Can children use it?
No. Children and teenagers need age- and sex-specific charts.
Is my data stored?
No. The calculation runs in your browser.
Ratings and comments
Loading…