BMI Calculator
Calculate your body mass index from height and weight in US or metric units, with your weight category and the healthy weight range for your height.
Body mass index (BMI) compares your weight with your height to give a single number used to screen adults for underweight, overweight and obesity. Enter your height and weight in US or metric units to see your BMI, the CDC weight category it falls into, and the weight range that would put you in the healthy band for your height.
How to use this tool
- Choose US units (feet, inches, pounds) or Metric (centimetres, kilograms).
- Enter your height. In US units, put feet in the first box and the remaining inches in the second.
- Enter your current weight.
- Read your BMI and category, then use the table to see the weight range for every category at your height.
Formula
BMI = weight (kg) ÷ height (m)² = 703 × weight (lb) ÷ height (in)²
The 703 factor turns pounds and inches into the metric result; this tool converts with the exact factors (1 lb = 0.45359237 kg, 1 in = 2.54 cm). Adult cut-offs: under 18.5 underweight, 18.5 to under 25 healthy weight, 25 to under 30 overweight, and 30 or more obesity, split into class 1 (30–34.9), class 2 (35–39.9) and class 3 (40 and above). BMI Prime is simply BMI ÷ 25. Classification uses the unrounded BMI; displayed boundary weights are rounded.
Example
At 5 ft 10 in (177.8 cm) and 160 lb (72.6 kg): height² = 1.778² = 3.161 m², so BMI = 72.57 ÷ 3.161 = 23.0, in the healthy weight range. At that height a BMI of 18.5 to under 25 corresponds to about 128.9 lb to under 174.2 lb, and the BMI Prime is 0.92.
Frequently asked questions
What is a healthy BMI for adults?
For adults 20 and older, 18.5 to under 25 is the healthy range used by the CDC and the World Health Organization. The same cut-offs apply to men and women of any adult age, although what a given BMI means for health can differ with age, sex and ethnicity.
Is BMI accurate for athletes or older people?
BMI cannot tell muscle from fat. Muscular people can be classed as overweight with little body fat, while older adults who have lost muscle may carry more fat than their BMI suggests. A waist measurement adds useful context.
Are the cut-offs different for Asian adults?
A WHO expert consultation found that many Asian populations have higher health risks at lower BMIs, and several countries use lower action points, such as 23 for overweight. Ask your doctor which cut-offs are used where you live.
Can I use this for children or during pregnancy?
No. Children and teens aged 2–19 need a BMI-for-age percentile, and BMI during pregnancy is not meaningful; pregnancy weight-gain advice is based on your BMI before pregnancy.
Sources
This tool gives an estimate for general information only. It is not financial, tax, legal or medical advice — check with a qualified professional before you rely on the result.
Last updated: 2026