BMI Calculator

Calculate adult BMI from height and weight, with its screening category. Enter your own values below to see body mass index and check the method behind it.

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Your inputs

Change the example values to match your situation.

Your result

Let’s work it out.

Fill in your inputs and select Calculate.
Your result and breakdown will appear here.

How this calculator works

BMI = weight in kg ÷ height in metres squared. WHO general adult cutoffs are shown; BMI does not directly measure body fat.

Before you use the result

  • Estimates for general information. They do not diagnose a condition or replace a qualified clinician’s assessment.

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What is BMI Calculator?

BMI Calculator helps you calculate adult BMI from height and weight, with its screening category.

The main result is body mass index, with a breakdown of WHO adult category. The formula, example and assumptions below explain how to interpret it.

How to use BMI Calculator

Use the example to get familiar with the form, then enter your own figures. Any rates in the example are illustrative. Check the field labels and units before calculating.

  1. Gather weight (kg) and height (cm). Use values from the same situation or reporting period.
  2. Replace the example weight with your own value, then complete the other fields. Check the displayed units.
  3. Select Calculate and read body mass index with its result breakdown. Change one input and calculate again to compare a second scenario. Reset restores the original example.
  • Enter weight in kg, at least 20 and at most 500. Decimals are accepted.
  • Enter height in cm, at least 100 and at most 250. Decimals are accepted.

BMI Calculator: a worked example

With the inputs below, the result is 24.221453 kg/m² (body mass index). Follow the example, then replace these illustrative values with your own.

Example inputs and output
Input or outputExample value
Weight (kg)70 kg
Height (cm)170 cm
Body mass index24.221453 kg/m²
WHO adult categoryNormal range

Understanding the BMI result

Read body mass index alongside WHO adult category. These describe different parts of the same calculation.

Displayed results use a readable number of decimal places. When checking a result by hand, keep extra precision until the last step. To compare scenarios, change one input at a time and keep the others fixed.

  • Example WHO adult category: Normal range

BMI Calculator: assumptions and common mistakes

A useful estimate starts with the right inputs. Check the following assumptions and limits before applying the result to your situation.

  • Estimates for general information. They do not diagnose a condition or replace a qualified clinician’s assessment.
  • Health estimates are context-dependent. Age, pregnancy, illness, medication and individual measurements can affect interpretation; these tools do not diagnose a condition.

For wider guidance, visit World Health Organization. The formula and scope of this specific tool are stated on this page.

BMI Calculator FAQs

What does BMI Calculator calculate?

BMI Calculator helps you calculate adult BMI from height and weight, with its screening category. Its main output is body mass index in kg/m².

What inputs do I need for BMI Calculator?

You need weight (kg) and height (cm). Use the field labels and units to match your figures to the formula.

Which formula does BMI Calculator use?

BMI = weight in kg ÷ height in metres squared. WHO general adult cutoffs are shown; BMI does not directly measure body fat.

What is a worked example for BMI Calculator?

Example inputs: Weight: 70 kg; Height: 170 cm. The result is 24.221453 kg/m² (body mass index).

How should I enter weight?

Enter weight in kg, at least 20 and at most 500. Decimals are accepted.

How do I choose height?

Enter height in cm, at least 100 and at most 250. Decimals are accepted. The example uses 170 cm; replace it if your circumstances differ.

How should I read body mass index?

Read body mass index alongside WHO adult category. These describe different parts of the same calculation.

Why might my BMI Calculator result differ from my records?

Estimates for general information. They do not diagnose a condition or replace a qualified clinician’s assessment. Differences in entered values, units or rounding can also change the comparison.

Can I compare two scenarios in BMI Calculator?

Yes. Note your first body mass index, change weight or another input, and select Calculate again. Editing a field clears the old result so it is not mistaken for a new calculation.

Is BMI Calculator free, and where are my inputs calculated?

This calculator is free to use without signing in. Its formula runs in your browser; calculator inputs are not sent to a calculation API. The inputs reset to the example values when you reset the form or start a fresh page.