# BMI calculator

URL: https://shahid09.is-a.dev/tools/bmi-calculator/
Author: Muhammad Shahid (https://shahid09.is-a.dev/)
Free tool · runs in your browser

Calculate your body mass index from your weight and height, and see your category and healthy weight range.

**Quick answer:** BMI is your weight in kilograms divided by your height in metres squared. So 70 kg at 1.75 m gives 70 ÷ 3.0625 = 22.9. The WHO adult categories are: under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, and 30 or more obesity. BMI is a screening number rather than a diagnosis, so talk to a doctor about your health.

## How to use it

1. **Choose your units.** Metric (kg and cm) or US (lb, feet and inches).
2. **Enter weight and height.** The result appears straight away.
3. **Read your result.** See your BMI, its category and the healthy weight range for your height.

## Example

An adult weighing 70 kg at a height of 175 cm:

Input:

```
Weight: 70 kg
Height: 175 cm
```

Output:

```
BMI: 22.9
Category: Healthy weight
Healthy range: 56.7 kg to 76.3 kg
```

## Common errors and how to fix them

- **My BMI looks far too high or low**: Check the units: 175 goes in as centimetres rather than metres, and pounds must not be entered as kilograms.
- **My BMI says overweight but I am muscular**: BMI cannot tell muscle from fat. A waist measurement or body-composition test gives a better picture.

## Frequently asked questions

### How is BMI calculated?

Metric: weight in kg ÷ (height in m)². US: 703 × weight in lb ÷ (height in inches)². The tool converts US units to metric and gives the same answer.

### What is a healthy BMI?

18.5 to 24.9 for most adults, according to the World Health Organization.

### Is BMI accurate?

It is a useful population-level screen, but it does not measure body fat directly. Muscular people can score high, and older people with little muscle can score low.

### Are the ranges different for Asian adults?

Often, yes. Health risks can begin at a lower BMI in many Asian populations, and a WHO expert group suggested extra action points at 23 and 27.5. Some countries use lower cut-offs.

### Can children use this calculator?

No. Under-20s need age- and sex-specific growth charts. Ask a paediatrician or use your health service's child calculator.

### Does BMI apply during pregnancy?

No. Weight changes in pregnancy make it unreliable. Doctors usually use your pre-pregnancy BMI.

### What else should I check besides BMI?

Waist measurement, blood pressure, blood sugar and cholesterol tell you more about health risk. A doctor can interpret them together.

### Is my data saved?

No. Your weight and height stay in your browser and are not stored or sent.

### How do I convert pounds and feet for BMI?

Choose US units and enter them directly. The tool converts them to kilograms and metres for you: 1 lb is 0.4536 kg and 1 inch is 2.54 cm.

### Does BMI change with age?

The adult formula is the same from age 20, although body composition changes with age. To check an exact age, use the [age calculator](https://shahid09.is-a.dev/tools/age-calculator/).

## Related

- [Age calculator](https://shahid09.is-a.dev/tools/age-calculator/)
- [Percentage calculator](https://shahid09.is-a.dev/tools/percentage-calculator/)
- [Basic calculator](https://shahid09.is-a.dev/tools/basic-calculator/)

## Sources

- [World Health Organization: Obesity and overweight](https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight)
- [CDC: Adult BMI categories](https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html)