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BMI Calculator

Check your body mass index in seconds. You also get the healthy weight range for your height, your BMI Prime and, if you add your waist, your waist-to-height ratio, a better guide to belly fat.

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Measure around your middle, halfway between your lowest rib and the top of your hip bone.

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Your body mass index
—kg/m²
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Healthy weight for your height
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Weight for your height
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BMI Prime (BMI ÷ 25)

BMI is a quick screening number, not a diagnosis. For muscle versus fat, estimate your body fat.

WHO BMI categories for adults

The same for men and women. Your row is highlighted.

CategoryBMI
UnderweightUnder 18.5
Healthy weight18.5–24.9
Overweight25–29.9
Obesity class I30–34.9
Obesity class II35–39.9
Obesity class III40 or more
Written by Updated Sources listed at the end

How BMI is calculated

BMI = weight (kg) ÷ height (m)²
US units: BMI = 703 × weight (lb) ÷ height (in)²
Worked exampleA man who is 180 cm tall and weighs 85 kg: 1.80 × 1.80 = 3.24, and 85 ÷ 3.24 = 26.2. That is in the overweight range. The healthy range for his height is 59.9–80.7 kg.

BMI was designed to compare groups of people, and it is still the standard first check used by doctors and public health bodies. Read the full background in Body mass index explained.

BMI for men

Many people search for a "BMI calculator for men" expecting a different formula. There isn't one: adult men and women use the same equation and the same categories. The difference is in what the number means. Men usually carry more muscle and less fat at the same BMI, so a muscular man can read as overweight while being lean. A 92 kg, 180 cm man who lifts weights has a BMI of 28.4, which the chart calls overweight, even if his body fat is low.

That is why this calculator adds two checks a plain BMI tool leaves out: your waist-to-height ratio, and a link to estimate body fat. For calories rather than categories, go to the TDEE calculator.

Asian cut-off points

A World Health Organization expert consultation found that many Asian populations have higher body fat and higher risk of type 2 diabetes and heart disease at lower BMIs than European populations. It suggested extra action points for public health: risk starts to rise from a BMI of 23, and is high from 27.5. The UK's National Institute for Health and Care Excellence (NICE) also uses lower thresholds for people of South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds.

BMIWHO standardAsian action points
Under 18.5UnderweightUnderweight
18.5–22.9HealthyHealthy
23–24.9HealthyIncreased risk
25–27.4OverweightIncreased risk
27.5–29.9OverweightHigh risk
30 and overObesityHigh risk

Where BMI falls short

  • It ignores muscle. Athletes and lifters often score as overweight.
  • It ignores where fat sits. Fat around the waist carries more health risk than fat on the hips and thighs.
  • It shifts with age. Older adults lose muscle, so the same BMI can hide more fat.
  • It does not apply to children, or during pregnancy.

Waist-to-height ratio

NICE advises adults with a BMI under 35 to also measure their waist-to-height ratio, and to keep their waist to less than half their height. A ratio of 0.5 to 0.59 means increased health risk, and 0.6 or more means high risk. It needs only a tape measure, and it picks up belly fat that BMI misses.

ExampleA 180 cm man with an 88 cm waist has a ratio of 88 ÷ 180 = 0.49, just under the 0.5 line. If his waist were 95 cm, the ratio would be 0.53, in the increased-risk band, even though his BMI did not change.

Related

Body mass index explainedRanges, history and limits.Body fat calculatorMuscle versus fat, with a tape measure.TDEE calculatorHow many calories you need.

Sources

  1. World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894. Geneva: WHO; 2000. iris.who.int
  2. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157–163. PubMed 14726171
  3. National Institute for Health and Care Excellence. Obesity: identification, assessment and management (CG189), waist-to-height ratio recommendations, 2022 update. nice.org.uk

Frequently asked questions

Is BMI different for men and women?
No. Adult BMI uses the same formula and the same categories for men and women: weight in kilograms divided by height in metres squared. What differs is body composition. At the same BMI, women usually carry more body fat than men, which is one reason BMI is only a rough screening tool.
What is a healthy BMI for a man?
For most adult men the healthy range is 18.5 to 24.9. If you are of South Asian, Chinese or other Asian background, health risk starts to rise at a lower BMI, from about 23, so the calculator lets you switch to the Asian cut-off points.
Why is my BMI high when I am muscular?
BMI cannot tell muscle from fat. A lean man who lifts weights can have a BMI over 25 with little body fat. Check your waist-to-height ratio or estimate your body fat with the body fat calculator for a clearer picture.
What is BMI Prime?
BMI Prime is your BMI divided by 25, the upper limit of the healthy range. A BMI Prime of 1.00 means you are exactly at the limit; 0.90 means 10% below it, and 1.10 means 10% above it.
Is this BMI calculator suitable for children?
No. Children and teenagers need age- and sex-specific BMI percentiles, which this calculator does not use. Ask a doctor or use a dedicated child BMI tool.