BMI Calculator: Check Your Body Mass Index for Free
Enter your height and weight and you get your body mass index to one decimal place, read against two published systems: the WHO standard bands and the lower WHO Asia-Pacific cut-offs.
Four easy steps
How to use this BMI calculator in about a minute
Nothing here needs a login or a clinic visit. You need a set of scales, a wall and something to measure height with.
Enter what you measured
Sex, age, height and weight. Pick metric, imperial or stone first so you are typing in the units you actually read off the scales. Prefilled values from the home page QuickStart appear automatically.
Read the number and both bands
You get your BMI to one decimal place, then the full classification table. Your row is marked under the WHO standard cut-offs and under the WHO Asia-Pacific cut-offs at the same time.
Check the what-if rows
We recalculate your BMI at plus and minus 2 kg, and at plus and minus 2 cm of the height you entered. If a small measurement slip moves you into another band, you will see it there.
Open the next tool prefilled
BMI cannot see fat, muscle or where weight sits. The result panel hands your figures straight to the waist, body fat and calorie tools so you do not retype anything.
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How we work
A clear path from first conversation to finished work.
Body composition calculators
BMI, Asian BMI, body fat, skinfold, relative fat mass, lean body mass, FFMI, ideal and healthy weight range, frame size and recomposition tools, each printing the classification systems side by side with stated error bands.
Fat distribution calculators
Waist circumference, waist to height ratio, waist to hip ratio, body roundness index and a visceral fat tape proxy, mapped to published thresholds and clearly labelled as tape measures rather than scan volumes.
Calorie and nutrition calculators
BMR, TDEE, calorie deficit and surplus, macros, protein, water, fibre, weight-loss time, check-in, reverse diet and alcohol tools, with intake floors, weekly rate caps and no finish-date countdowns.
Fitness calculators
Calories burned, walking and running energy cost from published MET values, heart rate zones, VO2 max field tests and one rep max estimates, shown gross and net where that distinction matters.
The proportion of Asian people with a high risk of type 2 diabetes and cardiovascular disease is substantial at BMIs lower than the existing WHO cut-off point for overweight of 25 kg/m2.
What BMI misses
Four things your BMI cannot tell you, and the tool that can
BMI is one ratio of two numbers. It cannot separate fat from muscle, it cannot see where weight sits, and it says nothing about how much you eat or burn.
Fat versus muscle
BMI counts a heavy, muscular build the same as a soft one. The Navy tape method gives a body fat percentage instead, with the honest error band of about 3 to 4 points against a DEXA scan.
Where the weight sits
Two people at BMI 27 can carry it very differently. Waist divided by height, healthy under 0.5, is the fastest check on abdominal fat and needs only a tape measure.
What you burn in a day
BMI has nothing to do with energy. TDEE estimates daily calorie needs from your BMR and activity level, printed with a plus or minus 12.5 per cent band rather than a false single figure.
A safe calorie target
If you have decided to lose weight, the deficit tool caps the rate at 1 per cent of bodyweight a week and holds intake floors. No finish date, no countdown clock.
05 — Common questions
Questions people ask about their BMI result
The ones we get most often, answered properly rather than in one line.
Frequently Asked Questions
- What is a healthy BMI range?
- Under the WHO standard bands, 18.5 to 24.9 is classed as healthy weight. Under the WHO Asia-Pacific cut-offs the healthy band is narrower, 18.5 to 22.9, with overweight starting at 23.0. Both appear on your result. A BMI inside either band is a screening result about a population, not a clean bill of health for one person.
- Why do your two tables disagree with each other?
- Because they were set for different populations. The 2004 WHO expert consultation found that risk of type 2 diabetes and cardiovascular disease rises at lower BMIs in many Asian populations, so the overweight line drops to 23.0 and obesity to 25.0. Rather than pick a winner, we print both columns and mark your number in each so you can see how much the label depends on the system used.
- Is BMI accurate if I lift weights?
- No. BMI uses total weight and cannot tell muscle from fat. A well-trained rugby player can land in the obese band on the standard table with low body fat. If you carry a lot of lean mass, treat BMI as background and use the Navy tape body fat calculator and your waist to height ratio instead, then track those two over time.
- Who should not use this BMI calculator?
- Anyone under 18, because children and teens are assessed on CDC age and sex percentiles, never adult cut-offs. Pregnant women, because weight gain is expected and is assessed against pre-pregnancy BMI using the IOM 2009 ranges. Also treat it loosely if you are a serious athlete, are frail or older with muscle loss, or have significant fluid retention.
- Does the 2025 obesity framework make BMI useless?
- No, it changes its job. The 2025 clinical obesity framework treats BMI as a screening step rather than a diagnosis, and asks for a second measure of body size such as waist circumference or waist to height ratio alongside it, plus signs of whether organ function or daily activity is affected. That is why every result here points you to the waist tools next.
- Does metric, imperial or stone change the answer?
- Not at all. Metric divides kilograms by height in metres squared. Imperial multiplies pounds by 703 and divides by height in inches squared. Stone is converted to pounds first. Our worked example gives 25.9 in all three. Pick whichever units you actually measure in, because you are less likely to make a conversion mistake typing what you read.
- Do you keep my height and weight?
- No. There are no accounts and no stored measurements. Your figures live in the page and in the query string of the link if you carry them to the next tool, and nothing is written to a server. Close the tab and the numbers are gone. This is also why nothing here is medical advice: it is a calculator with published cut-offs, not a consultation.
Get your number, then get the rest of the picture
Run your BMI above, then spend another minute on a waist measurement or your daily energy needs. Nothing on this site is medical advice, so take anything that worries you to your GP.