How to use the BMI calculator
- 1Choose Metric (cm, kg) or Imperial (ft, in, lb). Your choice is remembered.
- 2Enter your Height and Weight.
- 3Read Your BMI and its WHO category, the weight range that gives a BMI of 18.5–24.9 at your height, and the formula.
- 4Tick Also show WHO action points for Asian adults to see the lower Asian cut-offs alongside.
Metric and imperial
175 cm, 70 kg 5 ft 9 in, 160 lb
BMI 22.9 (Healthy weight); healthy range at 175 cm: 56.7–76.3 kg BMI 23.6 (Healthy weight)
Adult BMI categories
BMI is weight in kilograms divided by height in meters squared. The World Health Organization classifies adults as:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy (normal) weight |
| 25.0–29.9 | Overweight (pre-obesity) |
| 30.0–34.9 | Obesity class I |
| 35.0–39.9 | Obesity class II |
| 40.0 and above | Obesity class III |
The same cut-offs apply to men and women. The US CDC uses them from age 20.
Metric and imperial units
- Metric: BMI = kg ÷ m². 70 kg at 1.75 m: 70 ÷ 3.0625 = 22.9.
- Imperial: BMI = 703 × lb ÷ in². 160 lb at 69 in: 703 × 160 ÷ 4,761 = 23.6.
The 703 factor comes from the unit conversions (1 lb = 0.45359237 kg, 1 in = 0.0254 m); its exact value is 703.07. The calculator converts imperial inputs exactly, then rounds the BMI to one decimal place, as BMI charts do. A category is decided on the rounded value, so 24.96 shows as 25.0, Overweight.
Lower cut-offs for Asian adults
At the same BMI, many Asian populations have a higher percentage of body fat and a higher risk of type 2 diabetes and heart disease. A 2004 WHO expert consultation kept the international categories but proposed extra public-health action points: 23 (increased risk) and 27.5 (high risk). Several countries use lower cut-offs in their own guidance; for example, India's 2009 consensus guidelines treat 23–24.9 as overweight and 25 or more as obesity.
Tick the Asian action points option to see where your BMI falls on that scale.
Children and teens: BMI-for-age percentiles
Adult categories don't apply to anyone under 20 (CDC) or under 19 (WHO). Children's body fat changes with age and differs between boys and girls, so their BMI is compared with growth charts and expressed as a percentile for their age and sex. In the CDC charts, the 85th percentile and above is overweight and the 95th and above is obesity.
This calculator doesn't calculate percentiles. Use the CDC's child and teen BMI calculator or the WHO growth reference, and discuss the result with a pediatrician.
What BMI doesn't measure
BMI uses only height and weight, so it can't tell muscle from fat or show where fat is stored.
- Muscular people (athletes, manual workers) can have a high BMI with little body fat.
- Older adults can have a normal BMI with low muscle and more fat.
- Fat around the waist carries more health risk than the same weight elsewhere. A waist measurement, or waist-to-height ratio below 0.5, adds useful information.
BMI is a quick screening number for groups and a starting point for a conversation with a health professional, not a verdict on an individual's health.
Is anything I enter stored?
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