BMI Calculator
Enter your weight and height to get your BMI, its WHO adult category and the healthy weight range for your height.
What this tool does
BMI is your weight in kilograms divided by your height in metres squared. A BMI of 18.5 to 24.9 is the WHO healthy range for adults, under 18.5 is underweight, 25 to 29.9 is overweight and 30 or more is obesity. Enter weight and height to see yours and the weight range for your height.
Calculates BMI from your weight and height in metric or US units.
Shows the WHO adult category and the weight range that falls in the 18.5 to 24.9 band for your height.
How to use it
- Choose metric or US units.
- Enter your weight and height in the boxes for the units you chose.
- Read your BMI, category and healthy range.
- Remember BMI is a screening number, not a diagnosis.
Why use this calculator
Shows your BMI, the WHO adult category and the weight range that corresponds to the healthy BMI band for your height. BMI is the quickest standard way to compare weight with height, and it is used in health surveys and by many clinicians as a first screen. Seeing the weight range for your height is often more useful than the number alone.
Why we built it
We built the BMI calculator to show the WHO category and the weight range for your height, and to say plainly what BMI cannot tell you. Look at body composition with the body fat calculator, and your energy needs with the calorie calculator.
Related tools worth a look: the Ideal Weight Calculator, the Waist-to-Hip Ratio Calculator and the Grade Calculator.
Who this tool is for
- Adults wanting a quick screening number for weight and height
- Students and teachers in health and PE classes
- People preparing for a routine check-up conversation
When to use it
- Getting a first, rough read on weight relative to height.
- Checking a figure given by a doctor, a form or a gym.
- Setting a general weight goal range.
- Converting between metric and US body measurements.
How it works
BMI = weight (kg) ÷ height (m)². In US units the equivalent is 703 × weight (lb) ÷ height (in)². The WHO adult bands are: under 18.5 underweight, 18.5-24.9 healthy range, 25-29.9 overweight, 30-34.9 obesity class I, 35-39.9 class II and 40 or more class III.
Example: 70 kg at 175 cm is 70 ÷ 1.75² = 22.9, within the healthy range. The healthy weight range for 175 cm is 56.7 to 76.3 kg.
BMI does not measure body fat or fitness. It can overestimate in muscular people and underestimate in people with low muscle mass, and the cut-offs are interpreted differently for children, older adults, pregnancy and some ethnic groups.
A worked example
These are the values the calculator opens with, so you can see exactly what it does with them. Change any value on the page and the result updates; the figures below come from the same calculation.
| Input | Value |
|---|---|
| Units | Metric - kg and cm |
| Weight | 70 |
| Height | 175 |
| Weight | 154 |
| Height - feet | 5 |
| Height - inches | 9 |
With those inputs, the calculator returns:
- Body mass index: 22.9 kg/m²
- WHO adult category: Healthy weight range
- Healthy range for this height: 56.7 to 76.3 kg (125 to 168 lb)
- Weight: 70 kg
- Height: 175 cm
What you give it, and what you get back
| Item | Details |
|---|---|
| Units | Metric (kg, cm) or US (lb, feet, inches). |
| Weight and height | Your current weight and your height, entered in the boxes for the chosen units. |
| Output | BMI, WHO adult category and the healthy weight range for that height. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| Result seems wrong | Values were entered in the wrong unit boxes. | Check the units setting and the boxes you filled in. |
| I am an athlete and my BMI says overweight | Muscle is dense and BMI cannot tell it from fat. | Use waist measurement or body-fat estimates alongside BMI. |
| I am under 20 | The adult bands do not apply to children and teenagers. | Use age- and sex-specific growth charts from a clinician. |
| Category differs from my doctor's | Some guidance uses different cut-offs for some ethnic groups. | Follow your clinician's advice. |
Assumptions and limitations
- Adults aged 20 and over only.
- A screening measure: it does not diagnose or measure health.
- It does not account for muscle, bone density, age, pregnancy or ethnicity.
Frequently asked questions
How do I calculate my BMI?
Divide your weight in kilograms by your height in metres squared. Or enter your weight and height above and read the result.
What is a healthy BMI?
For most adults the WHO healthy range is 18.5 to 24.9.
Is BMI accurate?
It is a quick screening number. It is reasonable for large groups but it can mislead for individuals because it ignores muscle, fat distribution and age.
Is BMI the same for men and women?
The adult formula and bands are the same, although body composition differs between men and women on average.
Does it work for children?
No. Children and teenagers are assessed with growth charts that compare them with others of the same age and sex.
Is my information sent anywhere?
No. It is calculated in your browser.