BMI calculator
Your BMI, with WHO and Asian Indian cut-offs.
- WHO category
- Normal range
- Normal BMI range (WHO)
- 18.5–24.9
- Normal weight for your height
- 56.7–76.3 kg
For adults 18 and over; under 18, BMI is read on growth charts by age and sex. A screening number, not a diagnosis or medical advice. In pregnancy, or with a condition that affects your weight, ask your doctor.
This BMI calculator works out your body mass index from your weight and height, in kilograms and centimetres or pounds and inches. It places you on the WHO adult scale or the lower Asian Indian cut-offs, shows the normal weight range for your height and, if you add your waist, what that measure adds.
- Free, no sign-up
- Metric or imperial
- Runs in your browser; nothing is saved
How the calculator works →Coaching clients? Try Trainaq free →
What is BMI?
BMI, body mass index, is your weight in kilograms divided by your height in metres squared. This BMI calculator places the result on the WHO adult scale, where 18.5 to 24.9 is the normal range, or on the Asian Indian scale, where overweight starts at 23. BMI screens for excess weight; it does not measure body fat.
- WHO adult categories from the 2000 WHO obesity report
- Asian Indian cut-offs: overweight from 23, obesity from 25 (Indian consensus, 2009)
- The normal weight range for your height
- Optional waist measure and waist-to-height ratio
How it works
How does this BMI calculator work?
It divides your weight in kilograms by the square of your height in metres, after converting pounds and inches if you use them. It rounds the result to one decimal, finds your category on the scale you choose, and, if you enter your waist, compares it with the cut-offs for that scale.
Work out the index
BMI is weight divided by height squared: 70 kg at 1.75 m is 70 ÷ 3.0625, or 22.9. In pounds and inches the same sum is multiplied by 703, which is only the conversion between the two sets of units.
- Shown to one decimal, and classified as shown
- For adults, WHO’s cut-offs are the same at every age and for both sexes
Choose the cut-offs
The WHO scale is the international one. A WHO expert consultation in 2004 found that many Asian people are at high risk of type 2 diabetes and heart disease below a BMI of 25, and an Indian consensus in 2009 set overweight at 23 and obesity at 25 for Asian Indians.
- WHO kept its own cut-offs as the international classification
- The Indian cut-offs were written for Asian Indians
See the normal range for your height
The calculator turns the normal BMI range back into weights for your height: 18.5 to 24.9 on the WHO scale, or 18.5 to 22.9 on the Asian Indian one. At 175 cm, that is 56.7 to 76.3 kg, or 56.7 to 70.1 kg.
- The ideal weight calculator sets these beside four older formulas
Add your waist if you can
BMI cannot tell where fat sits. Waist circumference adds that. WHO’s example cut-offs, from a Dutch study, are 94 cm for men and 80 cm for women, and the Indian consensus uses 90 cm and 80 cm. A waist under half your height is a simple screening check.
- Measure midway between your lowest rib and the top of your hip bone
- Read the tape at the end of a normal breath out
Formula
Which formula does the calculator use?
The standard one: weight in kilograms divided by height in metres squared. In pounds and inches, it is 703 times weight divided by height squared, which gives the same number. The waist-to-height ratio divides your waist by your height in the same units, so it has no unit at all.
BMI = W ÷ H²BMI = 703 × Wlb ÷ Hin²W = BMI × H²WHtR = waist ÷ height- W: weight in kg; H: height in metres
- Wlb: weight in pounds; Hin: height in inches
- 703: the unit conversion, 0.4536 kg per lb ÷ 0.0254² m² per square inch
- WHtR: waist and height measured in the same unit
WHO categories
What are the WHO BMI categories for adults?
WHO classes adults as underweight below 18.5, normal from 18.5 to 24.9, pre-obese from 25 to 29.9 and obese from 30, in three classes. The same cut-offs apply to men and women of every adult age, though WHO notes that BMI may not mean the same fatness in every population.
| Category | BMI | Risk of comorbidities (WHO) |
|---|---|---|
| Underweight | Below 18.5 | Low, but risk of other clinical problems increased |
| Normal range | 18.5–24.9 | Average |
| Pre-obese | 25.0–29.9 | Increased |
| Obese class I | 30.0–34.9 | Moderate |
| Obese class II | 35.0–39.9 | Severe |
| Obese class III | 40 or more | Very severe |
Source: WHO Technical Report Series 894 (2000), Table 2.1, which groups a BMI of 25 or more as overweight. WHO’s fact sheet defines overweight as a BMI of 25 or more and obesity as 30 or more.
Asian and Indian adults
What are the BMI cut-offs for Asian and Indian adults?
An Indian consensus in 2009 set overweight at a BMI of 23 to 24.9 and obesity at 25 or more for Asian Indians, with abdominal obesity at a waist of 90 cm for men and 80 cm for women. WHO’s 2004 consultation suggested extra action points for Asian populations at 23, 27.5, 32.5 and 37.5.
| Measure | WHO (international) | Asian Indian (2009 consensus) |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Normal | 18.5–24.9 | 18.5–22.9 |
| Overweight | 25.0–29.9 | 23.0–24.9 |
| Obesity | 30 or more | 25 or more |
| Waist, men | 94 cm or more (increased risk) | 90 cm or more |
| Waist, women | 80 cm or more (increased risk) | 80 cm or more |
Sources: WHO TRS 894 (2000), Tables 2.1 and 2.2 (the waist levels are an example for Caucasians; WHO says waist cut-offs are population-specific); Misra et al. (2009), as restated in Misra et al. (2025), which gives the normal range as 18.5–22.99. WHO (2004) kept the international cut-offs and proposed ways for countries to set their own.
Worked example
What does a worked example look like?
Take someone who weighs 80 kg and is 180 cm tall. Their BMI is 80 ÷ 1.8², which is 80 ÷ 3.24, or 24.7. On the WHO scale that is the normal range, near its top. On the Asian Indian scale it is overweight, because overweight starts at 23 there.
- Normal weight at 180 cm: 59.9 to 80.7 kg on the WHO scale, or 59.9 to 74.2 kg on the Asian Indian one
- In imperial units, 154 lb at 5 ft 9 in: 703 × 154 ÷ 69², or 22.7
- With a 95 cm waist, a man is past WHO’s 94 cm level and the Indian 90 cm level; his waist-to-height ratio is 95 ÷ 180, or 0.53
What BMI misses
What does BMI miss?
BMI cannot tell muscle from fat, so very muscular people can read as overweight. Body fat percentage tends to rise with age up to about 60 to 65, women carry more fat than men at the same BMI, and the link between BMI and fat differs between ethnic groups. It also ignores where fat sits, which waist measures add.
- WHO calls BMI the most useful, albeit crude, population-level measure of obesity
- WHO’s 2004 consultation found Asian populations have different links between BMI, body fat and health risk than European ones
- People with extra fat around the abdomen are at particular risk, which is why waist measures help
- A body fat estimate tells you more about muscle and fat; try the body fat calculator
Waist
How do I use my waist measurement?
Compare it with the cut-offs for your scale. WHO’s example levels, from a Dutch study, are 94 cm for men and 80 cm for women for increased risk, and 102 cm and 88 cm for substantially increased risk. Indian guidance uses 90 cm and 80 cm. A waist under half your height is the simplest check.
- WHO’s protocol: measure midway between the lowest rib and the top of the hip bone, at the end of a normal breath
- In English survey data, a waist-to-height ratio of 0.5 or more picked out cardiometabolic risk better than BMI and waist together (Gibson and Ashwell 2020)
- In 2025, Indian experts proposed stage 2 obesity for a BMI over 23 with excess waist or waist-to-height ratio, plus related illness or limits on daily life
Limits
Can children and teenagers use this BMI calculator?
No. Under 18, BMI is read against growth charts for age and sex, because a healthy BMI changes as children grow. WHO classes children and teenagers by BMI-for-age on its growth reference, not by the adult cut-offs. Ask a doctor or nurse to check a child’s BMI and what it means.
- The calculator refuses ages under 18
- Pregnancy changes weight and waist, so neither the BMI categories nor the waist cut-offs apply
- Older adults: WHO notes body fat percentage rises with age up to 60 to 65
- Athletes: a heavy, muscular build can put you in the overweight range with little fat
For coaches
How do coaches use BMI with clients?
As one screening number among several. In Trainaq the intake form and weekly check-ins can ask for weight, height, waist and other measurements, in metric or imperial units, and the progress view shows the weight trend and the latest measurements, so you can follow how a client changes over time.
- The default weekly check-in asks for weight and waist
- Progress photos by pose sit beside the numbers
- Clients see their own weight chart in the Trainaq app
Sources
Sources
- WHO Consultation on Obesity. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894. Geneva: World Health Organization; 2000. Tables 2.1 and 2.2.
- World Health Organization. Obesity and overweight. Fact sheet.
- WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157–163.
- Misra A, Chowbey P, Makkar BM, et al. Consensus statement for diagnosis of obesity, abdominal obesity and the metabolic syndrome for Asian Indians and recommendations for physical activity, medical and surgical management. J Assoc Physicians India. 2009;57:163–170.
- Misra A, Vikram NK, Ghosh A, et al. Revised definition of obesity in Asian Indians living in India. Diabetes Metab Syndr. 2025;19(1):102989.
- World Health Organization. Waist circumference and waist–hip ratio: report of a WHO expert consultation, Geneva, 8–11 December 2008. Geneva: World Health Organization; 2011.
- Gibson S, Ashwell M. A simple cut-off for waist-to-height ratio (0·5) can act as an indicator for cardiometabolic risk: recent data from adults in the Health Survey for England. Br J Nutr. 2020;123(6):681–690.
FAQ
BMI calculator FAQ
Is BMI accurate?
Your BMI is exact arithmetic; what it says about your health is rough. WHO calls it the most useful, albeit crude, population-level measure of obesity. It cannot tell muscle from fat or show where fat sits, so pair it with your waist measurement and, if you can, a body fat estimate.
Why are the BMI cut-offs lower for Indians?
Because Asian Indians tend to carry more body fat and more abdominal fat at a given BMI, and type 2 diabetes appears at lower BMIs. The 2009 Indian consensus said that, on body fat and illness data, the limits of normal BMI are narrower and lower in Asian Indians than in white people.
What is a healthy BMI?
On the WHO scale the normal range for adults is 18.5 to 24.9. For Asian Indian adults, Indian guidance puts the top of the normal range at 22.9. Being in range does not rule out risk, so check your waist as well, and ask your doctor about your own health.
Does BMI work for muscular people?
Often not. BMI counts all weight the same, and WHO notes it does not distinguish weight from muscle and weight from fat. A strength athlete with little fat can sit in the overweight range. For muscular people, a waist measurement or a body fat estimate says more than BMI alone.
Is BMI different for men and women?
The formula and the cut-offs are the same for adult men and women: WHO states its values are the same for both sexes and do not depend on age. What differs is the meaning, because women carry more body fat than men at the same BMI. Waist cut-offs do differ by sex.
