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BMI Calculator

BMI Calculator is part of Toolspire and is ready as soon as this page loads. Work out your body mass index in seconds — in feet and inches or centimetres, kilograms or pounds. See your category on the WHO or Asian scale, the healthy weight for your height and how far you are from it.

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What you can do here

Feet and kilos together

Enter height in feet and inches and weight in kilograms — the way most people in India know them — or any other mix of units.

Asian and Indian cut-offs

One tap switches to the lower thresholds recommended for people of Asian descent, who face higher health risks at a lower BMI.

Your healthy weight range

See the exact weight range that gives a healthy BMI at your height, and the weight for every other category too.

Waist-to-height ratio

Add your waist size to check belly fat — a better guide to heart and diabetes risk than BMI alone.

Shows the working

The formula is written out with your numbers, so you can check the result by hand.

Private

Your height, weight and age are not sent to us, stored or shared.

The sequence

How to calculate your BMI

  1. 1

    Enter your height

    Type your height in feet and inches, or switch to centimetres.

  2. 2

    Enter your weight

    Type your weight in kilograms, or switch to pounds. Weigh yourself in the morning, in light clothes, for the most consistent number.

  3. 3

    Choose the categories

    Keep WHO (international), or pick Asian / Indian if you are of South Asian, Chinese or other Asian descent. Add your age and waist size for more context.

  4. 4

    Read your result

    See your BMI and category on the scale, your healthy weight range and how far you are from it.

Worth knowing

  • BMI Calculator on Toolspire: BMI = weight in kg ÷ (height in m)². In pounds and inches the same formula is 703 × lb ÷ in².
  • WHO adult categories: below 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight and 30 or more obesity (classes I, II and III from 30, 35 and 40).
  • Asian cut-offs (WHO Asia-Pacific classification, also used by Indian guidelines): 18.5–22.9 healthy, 23–24.9 overweight and 25 or more obesity.
  • Shows the healthy weight range for your height and how much you would need to lose or gain to reach it.
  • Optional waist-to-height ratio, graded with the NICE (2022) boundaries: 0.4–0.49 healthy, 0.5–0.59 increased health risk, 0.6 or more high risk.
  • Adult categories apply from age 18. Under 18, BMI has to be read on age- and sex-specific growth charts.
  • Height in feet and inches or cm, weight in kg or pounds, in any combination. Nothing you enter leaves your browser.

BMI chart for adults

CategoryWHO (international)Asian / Indian
UnderweightBelow 18.5Below 18.5
Healthy weight18.5 – 24.918.5 – 22.9
Overweight25.0 – 29.923.0 – 24.9
Obesity30.0 or more25.0 or more

How BMI is calculated

Divide your weight in kilograms by your height in metres squared. For someone who weighs 68 kg and is 1.70 m tall: 68 ÷ (1.70 × 1.70) = 68 ÷ 2.89 = 23.5.

In pounds and inches, multiply by 703: for 150 lb and 5 ft 5 in (65 in), 703 × 150 ÷ 65² = 105,450 ÷ 4,225 = 25.0. The calculator uses exact unit conversions, so both methods agree.

Why Asians have lower BMI cut-offs

At the same BMI, people of South Asian descent tend to carry more body fat, especially around the waist, and develop type 2 diabetes and heart disease at a lower BMI than people of European descent.

That is why the WHO Asia-Pacific classification and Indian consensus guidelines treat a BMI of 23 as overweight and 25 as obesity. If you are of Asian descent, a BMI of 24 is a reason to act, even though it is “healthy” on the international scale.

What BMI doesn’t tell you

  • Muscle vs fat: muscular people and athletes can have a high BMI without excess fat.
  • Where fat sits: fat around the waist carries more risk. Your waist should be less than half your height.
  • Older adults: muscle is lost with age, so body fat can be higher than BMI suggests.
  • Pregnancy: BMI isn’t valid during pregnancy; use your pre-pregnancy weight when a doctor asks for it.
  • Children and teens: BMI is compared with others of the same age and sex on growth charts rather than with the adult categories.

FAQ

Questions about BMI Calculator

Where does BMI Calculator run?

BMI Calculator runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

What is a healthy BMI?

For adults, 18.5 to 24.9 on the WHO scale. For people of Asian descent, including Indians, the recommended healthy range is 18.5 to 22.9.

Which cut-offs should I use if I’m Indian?

The Asian / Indian cut-offs. Indian consensus guidelines count a BMI of 23–24.9 as overweight and 25 or more as obesity, because health risks rise at a lower BMI in South Asians.

How is BMI calculated?

Weight in kilograms divided by height in metres squared. For example, 68 kg ÷ (1.70 m)² = 23.5. In imperial units, BMI = 703 × weight in pounds ÷ height in inches squared.

Is BMI accurate?

It is a quick screening measure that works well for most adults, but it can’t tell fat from muscle or show where fat is stored. Pair it with your waist-to-height ratio, and speak to a doctor about your overall health.

Is BMI different for men and women?

No. Adults use the same formula and categories for both sexes, although women naturally carry more body fat than men at the same BMI.

Can I use this calculator for children?

The BMI number is calculated the same way, but children and teenagers under 18 must be assessed on age- and sex-specific growth charts, not the adult categories. Enter an age under 18 and the calculator will tell you so.

What is BMI Prime?

Your BMI divided by the upper limit of the healthy range (25, or 23 on the Asian scale). A value above 1.00 means overweight; 1.20 means 20% above the limit.

What is a healthy waist-to-height ratio?

Keep your waist to less than half your height: a ratio of 0.4–0.49 is healthy, 0.5–0.59 means increased health risk and 0.6 or more means high risk (NICE, 2022).

Is my data saved?

No. The calculation runs in this tab, and your height, weight and age are never sent anywhere.

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