BMI Calculator
And the weight that matches your height.
Check the numbers you entered.
Add your waist circumference (optional)
This is the one that says the most of the two: it looks at where the fat is, which is what's linked to risk, and BMI can't see that. Sex is needed because WHO's thresholds are published separately for men and women.
Optional. If you have a tape measure handy, measure standing up at belly-button level, without pulling tight: waist circumference predicts cardiometabolic risk better than BMI does.
100% private — calculations happen on your device. Your weight, height, and waist are never sent to any server.
BMI is not a diagnosis and this page is not medical advice. It's a ratio between two numbers, weight and height, invented to describe populations rather than to judge one individual: it can't tell muscle from fat and doesn't know where that fat sits. It doesn't apply under 18, during pregnancy or breastfeeding, to very muscular people, and from 65 onward the range linked to lower mortality shifts upward. The thresholds are WHO's for the adult European population; Asian populations use lower figures. Your doctor, not a calculator, is who can read your numbers alongside the rest of your history.
Weight for each height, by BMI
The formula in reverse: the weight in kg that gives a BMI of 18.5, of 25, and of 30 at each height. The row for your height highlights itself when you use the calculator above.
| Height | BMI 18.5 to 25 | Obesity, from |
|---|---|---|
| 1.50 m | 41.6 – 56.3 kg | 67.5 kg |
| 1.55 m | 44.4 – 60.1 kg | 72.1 kg |
| 1.60 m | 47.4 – 64.0 kg | 76.8 kg |
| 1.65 m | 50.4 – 68.1 kg | 81.7 kg |
| 1.70 m | 53.5 – 72.3 kg | 86.7 kg |
| 1.75 m | 56.7 – 76.6 kg | 91.9 kg |
| 1.80 m | 59.9 – 81.0 kg | 97.2 kg |
| 1.85 m | 63.3 – 85.6 kg | 102.7 kg |
| 1.90 m | 66.8 – 90.3 kg | 108.3 kg |
| 1.95 m | 70.3 – 95.1 kg | 114.1 kg |
The weights come from multiplying 18.5, 25, and 30 by height in meters squared, rounded to one decimal. Overweight starts exactly where the middle column ends, so no extra column is needed for it. These are twenty-kilogram-plus ranges on purpose: very different builds fit inside them, and none of these numbers know how much of your weight is muscle.
How to use it
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1. Weight and height
Your weight from the scale and your height are all it takes. Switch the height unit in the dropdown next to it: the number converts itself, so 175 cm becomes 1.75 m without you having to retype it.
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2. Look at the range, not just the number
Below your BMI is what almost no calculator shows: the weight that gives a BMI of 18.5 to 25 at your height. It's the same formula flipped around, and it answers the question people actually come here with.
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3. If you have a tape measure, use it
Waist circumference is optional and sits below the result, but it's the figure that says the most: it predicts cardiometabolic risk better than BMI. Stand up, measure at belly-button level, don't pull tight.
BMI was invented by an astronomer, and not for you specifically
The body mass index dates to 1832 and its author was Adolphe Quetelet, a Belgian who was an astronomer, mathematician, and statistician — and not a doctor. What he was doing was describing l'homme moyen, the average man: he was looking for a way to summarize how height and weight were distributed across an entire population, and found that in adults, weight grew roughly with the square of height. That observation — a statistical regularity across thousands of people — is the entire foundation of the number that today comes up in doctor's offices and gyms.
The current name arrived a hundred and forty years later. In 1972, physiologist Ancel Keys compared several simple indexes of relative weight and concluded that Quetelet's performed best; he's the one who named it the body mass index. And he proposed it explicitly for population studies, warning that as a measure of one individual it had limits. That warning came built in — it just got lost along the way, the same way the second half of the sentence behind "eight glasses of water a day" got lost.
None of that makes it useless. For comparing populations, tracking trends, or a cheap first screen at a check-up, BMI works: it takes a scale and a tape measure, costs nothing, and correlates reasonably with body fat on average. The problem starts when a number meant for averages gets read as a verdict on one person.
What BMI can't see
It can't tell muscle from fat. BMI only knows two numbers, your weight and your height, and muscle weighs more than fat at the same volume. A rugby player, a powerlifter, or anyone who's spent years training strength can land in the "obesity" box with a low body fat percentage. And the reverse: a sedentary person with little muscle mass can have a perfectly centered BMI and considerably more fat than that number suggests.
It doesn't know where the fat is, which is exactly what matters. Fat surrounding the organs inside the abdomen is linked to considerably more cardiovascular and metabolic risk than fat stored on the hips and thighs. Two people with the same weight and height have the same BMI, however they carry it. A scale can't tell the difference; a tape measure can.
It doesn't know anything else. It doesn't know your blood pressure, your glucose, your cholesterol, your fitness, what you eat, or how much you move — and any one of those says more about your health than the ratio between your weight and the square of your height.
That's why there's a tape measure on this page
Waist circumference is the at-home measurement that best predicts cardiometabolic risk, and it costs what a sewing tape costs. WHO, in its 2008 expert consultation on waist circumference, for a European population, sets two steps:
- Elevated risk: from 94 cm in men and 80 cm in women.
- Very high risk: from 102 cm in men and 88 cm in women.
Measure standing up, tape horizontal at belly-button level, at the end of a normal exhale, without pressing into the skin. Like all population thresholds, these mark where average risk starts climbing, not where a disease begins — nobody wakes up sick going from 93 to 94 cm. But if your BMI says one thing and your waist says another, the waist wins.
The weight range is the formula in reverse
The question almost everyone actually has isn't "what's my BMI?" but "how much should I weigh for my height?". And that's answered with the same formula solved the other way: if BMI = weight ÷ height², then weight = BMI × height². Just plug in both ends of the range:
- For 1.75 m: 18.5 × 1.75² = 56.7 kg and 25 × 1.75² = 76.6 kg.
- For 1.65 m: 18.5 × 1.65² = 50.4 kg and 25 × 1.65² = 68.1 kg.
These are twenty-kilogram-plus ranges, and that width isn't a flaw in the math — it's just how it works out. Very different bodies fit inside it, with different skeletons and different amounts of muscle, and the range doesn't say which of all those weights is yours. It says where the band sits that, on average and across populations, is linked to lower mortality.
The thresholds don't hold equally for everyone
The 18.5 · 25 · 30 table is often presented as if it were universal, and WHO itself acknowledges it isn't. In Asian populations, cardiometabolic risk shows up at lower figures — at the same BMI, a higher body fat percentage and more risk — so thresholds of 23 for overweight and 27.5 for obesity are used instead of 25 and 30. Waist-circumference thresholds also change by geographic origin; the ones this page uses are the European ones.
And there are entire groups the table simply doesn't apply to: people under 18, who are assessed with age- and sex-specific percentiles because a growing body changes proportions; pregnant and breastfeeding women; very muscular people. From age 65 onward, the range linked to lower mortality shifts upward, so a BMI that would be labeled overweight in a younger adult may, at that age, be exactly where it's best to be.
What to do with the number
Not much, and calmly. BMI is a screening figure: it's useful for deciding whether something is worth a closer look, not for concluding anything on its own. If yours falls outside the range, what it gives you is a question — is it worth checking your waist, your blood pressure, your bloodwork — not an answer. If it falls inside, that's not a certificate of anything either: you can sit right in the middle of the table and still have bad bloodwork.
This calculator isn't going to tell you what to do, because it can't know that: it hasn't seen you, doesn't know your history, and isn't your doctor. All it does is give you the numbers done right and tell you where they come from. More free tools are on their way to the English section of Calculoteca.
Frequently asked questions
How is BMI calculated?
Divide weight in kilograms by height in meters squared. For 70 kg and 1.75 m: 1.75 × 1.75 = 3.0625, and 70 ÷ 3.0625 = 22.86, shown as 22.9. Height goes in meters, not centimeters: dividing by 175 squared gives a number ten thousand times too small and meaningless.
What's the normal weight for my height?
It's the BMI formula in reverse: the weight that gives a BMI of 18.5 is 18.5 × height², and the one that gives 25 is 25 × height². For 1.75 m that's 56.7 to 76.6 kg; for 1.65 m, 50.4 to 68.1 kg; for 1.80 m, 59.9 to 81.0 kg. It's a wide range on purpose, because very different builds fit inside it, and it says nothing about how much of that mass is muscle.
Where does BMI come from?
From Adolphe Quetelet, a Belgian astronomer and statistician who in 1832 was trying to describe the "average man" of a population and found that adult weight grew roughly with the square of height. He wasn't a doctor and wasn't measuring anyone's health — he was describing populations. The name "body mass index" was given by Ancel Keys in 1972, who proposed it precisely because of how well it behaved in population studies, while warning about its limits as a measure of one individual.
Is BMI useful for athletes?
Not really. BMI only knows how much you weigh and how tall you are — it can't tell a kilogram of muscle from a kilogram of fat. Since muscle is denser, a very muscular person can score a high BMI and land in the obesity category despite a low body fat percentage. The reverse also happens: someone with little muscle mass can have a BMI within range and a fair amount of fat. If you train strength seriously, BMI tells you little.
Why does waist size say more than BMI?
Because it looks at where the fat is, and that's the whole difference. Fat surrounding the abdominal organs is linked to considerably more cardiovascular and metabolic risk than fat stored on the hips or thighs. BMI can't see this: two people with the same weight and height have the same BMI no matter how they carry that fat. A three-dollar tape measure gives you information the scale simply doesn't have.
How big should my waist be?
WHO's 2008 expert consultation, for a European population, places elevated risk from 94 cm in men and 80 cm in women, and very high risk from 102 cm in men and 88 cm in women. Measure standing up, tape at belly-button level, at the end of a normal exhale, without pulling tight. These are population thresholds: they mark where average risk starts climbing, not where a disease begins.
Does BMI work the same for everyone?
No, and WHO itself acknowledges it. In Asian populations, cardiometabolic risk appears at lower figures, so thresholds of 23 for overweight and 27.5 for obesity are used instead of 25 and 30. Waist-circumference thresholds also shift by geographic origin. The ones on this page are for a European population.
Does BMI apply to children, pregnancy, or people over 65?
No, in none of the three cases. Under 18, these thresholds aren't used — age- and sex-specific percentiles are, because a growing body changes proportions. During pregnancy and breastfeeding, weight gain is part of the process and isn't read against this table. And from 65 onward, the range linked to lower mortality shifts upward, so a BMI that would be called overweight in a younger adult may not be at that age. It also doesn't apply to very muscular people.
Do you store my data?
No. Every calculation happens inside your own browser. Neither your weight, your height, your waist, nor anything else you type ever leaves your device: there's no server receiving it and no database storing it. You can check this by switching on airplane mode and seeing the calculator keep working.