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    BMI calculator

    Work out your BMI and what it says about you: the healthy weight for your height, whether your waist backs up the BMI, how much energy you need a day and where you stand among people of your age in your country.

    Health

    Everything is computed in your browser. Your height, weight and measurements are not sent anywhere.

    Sex
    For adults (18 and over). Your age is needed for the energy and the comparison.
    Waist and body fat (optional)
    Measure midway between the lowest rib and the top of the hip bone, after breathing out normally.
    Just below the larynx. Needed for the body fat estimate.
    At the widest point. Needed for a woman's body fat estimate.
    Energy, target weight and comparison
    Leave it empty to use the nearest limit of the healthy weight.

    Enter your height and weight to see your BMI. With your age come the energy and the comparison, with your waist the risk check.

    The new BMI

    The Oxford mathematician Nick Trefethen proposed a new body mass index: 1.3 × weight / height to the power 2.5. The usual BMI divides the weight by the height squared, so tall people get a slightly too high figure and short people a slightly too low one. At 1.69 m both are the same. Trefethen himself stresses that the new formula is not based on epidemiological studies, so read it beside the usual BMI, not instead of it.

    BMI classes

    Underweight under 18.5
    Healthy weight 18.5–24.9
    Overweight 25.0–29.9
    Obesity class I 30.0–34.9
    Obesity class II 35.0–39.9
    Obesity class III 40 and over

    Results are informational. Calculation is based on your input and public rules, official accounting may differ. For accuracy, confirm the final result if needed from the appropriate official source or specialist. See the terms of use.

    How it works?

    BMI is the weight in kilograms divided by the height in metres squared. The class is read from the figure shown on the page, with one decimal (WHO classes). The new BMI (Nick Trefethen) is 1.3 × weight / height to the power 2.5: a little lower for tall people and a little higher for short ones.

    Waist-to-height ratio is the waist divided by the height: under 0.5 there is no added risk, 0.5 to 0.59 the risk is increased and from 0.6 it is clearly increased. The waist measures apply under a BMI of 35.

    Energy: resting energy by the Mifflin-St Jeor equation, the daily need is that times your activity level (the 2001 FAO, WHO and UN University table). The time to a target weight is counted at 0.5 kg a week, a kilogram is about 7,700 kcal and a day is never counted at under 1,200 kcal.

    Body fat is an estimate by the US Navy circumference formula. The comparison comes from Eurostat's EU-SILC 2025 survey, where people gave their own height and weight.

    Everything is computed in your browser. Your height, weight and measurements are not sent to a server or stored.

    Frequently asked questions

    How do I calculate BMI?

    Divide your weight in kilograms by your height in metres squared. For example 72 kg and 1.75 m: 72 / (1.75 × 1.75) = 72 / 3.0625 = 23.5. The calculator does this for you and shows the class too.

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    What is a healthy BMI?

    By WHO's classes an adult's healthy weight is a BMI of 18.5 to 24.9, overweight 25 to 29.9 and obesity from 30. Over 65, a BMI of 23 to 29 goes with the lowest mortality (the Estonian guideline of 2026). The calculator shows what weight that is for your height.

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    Why can BMI be wrong?

    BMI does not tell muscle from fat. Someone who trains a lot may come out overweight with little fat, and a normal BMI can hide a lot of fat round the middle. So measure your waist too: a waist-to-height ratio over 0.5 means a higher health risk. The Estonian guideline calls the ratio a stronger sign of risk on its own than BMI.

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    What is the new BMI?

    The Oxford mathematician Nick Trefethen proposed 1.3 × weight / height to the power 2.5. The usual formula gives tall people a slightly too high figure and short people a slightly too low one, and the new one corrects that. Trefethen himself says it is not based on epidemiological studies, so it is an interesting extra figure, not a new standard.

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    How much should I eat to lose weight?

    The calculator works out your resting energy and your daily need from your activity. 0.5 kg a week means about 550 kcal a day less. Under 1,200 kcal a day is not recommended without a doctor's supervision, so when the sum would go below that, the calculator shows a longer time instead. The figure is approximate, as people burn energy differently.

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    Is my data stored?

    No. The calculator computes everything in your browser. Your height, weight and measurements do not go to a server, the address or the statistics, and they are gone when you close the page.

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    Where does the comparison with other people come from?

    From Eurostat's EU-SILC 2025 survey: how many of the men and women of each age group in each country are underweight, of healthy weight, overweight or obese. People gave their own height and weight, so the real share of overweight is usually a little higher.

    Link to this answer

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