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BMI Calculator

Work out body mass index from height and weight, in metric or imperial, with the arithmetic shown.

  • Unlimited
  • No signup
  • Private
  • Works offline

Calculate your BMI

Unit system
Measurements
How this was calculated

BMI = weight (kg) / height (m)²

= 74.5 / (1.78 × 1.78)

= 74.5 / 3.1684

= 23.5

Your BMI

23.5kg/m2

Normal
23.5
23.5
Underweight
< 18.5
Normal
18.5 - 24.9
Overweight
25.0 - 29.9
Obese
>= 30.0

Healthy weight range for 178 cm: 58.6 - 78.9 kg

How it works

  1. 01

    Pick your units

    Metric takes centimetres and kilograms. Imperial takes feet, inches and pounds.

  2. 02

    Enter height and weight

    The result updates as you type. Age and sex are optional and do not change the number.

  3. 03

    Read the working

    The page shows every step of the sum, so you can check the result yourself.

How BMI is calculated

BMI is your weight in kilograms divided by the square of your height in metres. In imperial units it is weight in pounds × 703 ÷ height in inches squared. Nothing else goes into it. Age and sex are optional here and never change the number. An age under 20 only tells you that the adult bands do not apply.

The formula uses total weight, so it cannot tell muscle from fat. A trained athlete and an inactive adult of the same height and weight get the same BMI. It is a screening ratio for whole populations. It works as a first check, but it cannot diagnose anything.

Units
Metric (cm / kg) and imperial (ft-in / lb).
Precision
Result rounded to one decimal place.
Categories
WHO adult ranges. Children use age-and-sex percentiles instead.
Stored data
None. Values stay in the page and clear on reload.

Reading the result

The scale beside the result marks the four adult WHO bands. A result near a boundary matters less than how your BMI changes over several months. One reading is not very exact either. Measure your height 1 cm wrong and the result moves by about 0.3.

Frequently asked questions

Is BMI accurate for everyone?
No. It is a screening ratio and does not measure what your body is made of. It tends to overstate the risk for muscular people and understate it for people with little muscle. Your waist size and body-fat percentage tell you more. Children and teenagers need age-and-sex percentile charts, because the adult bands do not fit them.
Do you store the height and weight I enter?
No. The values stay in the page, which never sends them to a server. A reload clears them.
Which BMI categories do you use?
The result uses the four WHO adult bands: underweight, normal, overweight and obese.
Can I calculate BMI in feet, inches and pounds?
Yes. Select Imperial above the form to enter height in feet and inches and weight in pounds.
Does the calculator work offline?
Yes. Once the page has loaded, your browser does all the arithmetic.
Is there a limit on how many calculations I can run?
No. There is no account, daily limit or usage counter.

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