BMI Calculator
Your BMI with the number placed on the category scale, in metric or imperial.
- Healthy range for your height
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- To reach it
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Free forever, no sign-up and no limits, and this tool installs on its own so you can keep it on your home screen.
Enter your height and weight in metric or imperial and get your BMI with the number placed on the category scale, not just printed. It also gives the weight range that would put you in the healthy band for your height, and how far you are from it. BMI is a rough screening figure and the page is clear about what it cannot see.
How to use it
- Choose your unitsMetric or imperial. Feet and inches are separate fields.
- Enter height and weightThe figure updates as you type.
- Read the scaleThe marker shows where your number falls, with the healthy range for your height underneath.
The scale is the point
A BMI of 26 means nothing on its own. What people actually want to know is whether that is a little over or a lot, and how far the healthy range is from where they are. So the number is placed on a banded scale with the boundaries marked, and the healthy weight range for your height is worked out and shown in the units you are already using.
The distance is often the useful figure. Being three kilograms above the band and being twenty are very different situations that produce BMI numbers only a few points apart.
What the formula can and cannot see
Height and weight are all it has. It cannot see muscle, bone density, how much of the weight is water, or where any of it sits. That last one matters most: fat around the abdomen behaves differently from fat on the hips, and BMI is blind to the difference. A waist measurement takes ten seconds and adds information BMI cannot.
This is not a reason to ignore it. Across large groups BMI tracks health outcomes well, which is why it survives. It is a reason not to read a single point of movement as meaningful.
Where the cut points came from
The 18.5, 25 and 30 boundaries are conventions adopted by the WHO, chosen because that is roughly where population level risk starts to rise. They are round numbers standing in for a smooth curve, so nothing changes about your body when you cross one. Somebody at 24.9 and somebody at 25.1 are in the same situation and in different categories, and the scale on this page is drawn to make that obvious rather than to hide it.
Units, done properly
Half the people looking this up think in stones or pounds and feet, and a calculator that only takes centimetres loses them at the first field. Both systems are here, converted through exact factors, so the two give the same answer rather than drifting apart in the third decimal.
Questions people ask
What is a healthy BMI?
Between 18.5 and 25 for adults, by the World Health Organization cut points. Below 18.5 is classed as underweight, 25 to 30 as overweight and above 30 as obese. A BMI of exactly 25 is still inside the healthy band; overweight starts above it, which is a detail some calculators get backwards.
How is BMI calculated?
Weight in kilograms divided by height in metres squared. That is the whole formula, published by Adolphe Quetelet in the 1830s as a way of describing populations. Imperial input is converted rather than run through a different formula, so the two agree.
Why is BMI criticised?
Because it cannot tell muscle from fat, and it does not know where the weight sits. A muscular athlete can score as overweight while carrying very little fat, and someone with a low BMI can carry a lot of it around the middle, which is the placement most associated with risk. It was designed to describe groups, not individuals, and using it as a personal verdict asks more of it than it can give.
Is BMI different for men and women?
The formula and the adult cut points are the same. Body composition differs on average, so the same BMI usually means a different amount of body fat, which is one reason a body fat estimate is a useful second look.
Does BMI work for children?
No, not with these numbers. Children are assessed on age and sex specific percentile charts, because normal body composition changes a great deal through growth. This tool is for adults.
Do the thresholds differ by ethnicity?
Several health bodies use lower cut points for people of South Asian, Chinese and some other backgrounds, because risk appears at a lower BMI in those populations. The figures shown here are the general WHO ones. If a lower threshold applies to you, your doctor will say so.
What should I do with the number?
Treat it as one input among several. If it sits well outside the healthy band it is worth a conversation with a doctor, who can also look at waist measurement, blood pressure and blood tests. A number from a web page is a prompt, not a diagnosis.