# BMI Calculator

URL: https://speedycalculator.com/calculators/health/bmi/
Last updated: 2026-10-25

> The BMI calculator divides your weight in kilograms by your height in metres squared and places the result in the standard adult categories: underweight below 18.5, healthy 18.5–24.9, overweight 25–29.9 and obesity 30 or more. It also shows the weight range that matches a healthy BMI for your height.

## Inputs

- Weight (kg, lb, st, g)
- Height (cm, m, in, ft)

## Results

- Body mass index — Type a target BMI to see the matching weight.
- Healthy weight from
- Healthy weight to

## Formula

```
BMI = weight (kg) ÷ height (m)²
```

## Explanation

Body mass index is a quick screening measure used worldwide to compare weight with height. It is cheap and easy, but it does not measure body fat directly.

### How to use it

Enter your weight and height in any unit; switching units keeps your value. Type a target BMI into the result to see the weight that would give it.

### Adult BMI categories

- Below 18.5: underweight
- 18.5 to 24.9: healthy weight
- 25 to 29.9: overweight
- 30 and above: obesity

### Limitations

BMI can overestimate fat in muscular people and underestimate it in older adults. Some populations, including many South Asian groups, face higher health risk at lower BMI values. Children and teens need age- and sex-specific percentiles instead. Combine BMI with waist measurement and a clinician’s advice.

### Inputs explained

FieldWhat to enterWeightUnits: kg, lb, st, gHeightUnits: cm, m, in, ft

### What each result means

- **Body mass index** = [Weight] ÷ ([Height]÷100)^2
- **Healthy weight from** = 18.5 × ([Height]÷100)^2
- **Healthy weight to** = 24.9 × ([Height]÷100)^2

### Example values

How the main result changes when **Weight** changes and everything else stays at the example values above:

Weight (kg)Body mass index (kg/m²)3511.452.517.17022.987.528.610534.314045.7

## Worked example

Weight 70 kg, height 175 cm (1.75 m).

BMI = 70 ÷ 1.75² = 70 ÷ 3.0625 ≈ **22.9**, healthy weight.

Healthy range for 1.75 m: 18.5 × 3.0625 ≈ 56.7 kg to 24.9 × 3.0625 ≈ 76.3 kg.

## Key terms

- **BMI**: Body mass index, weight divided by height squared, in kg/m².
- **Healthy weight range**: Weights that give a BMI from 18.5 to 24.9 at a given height.
- **Waist circumference**: A complementary measure of abdominal fat linked to health risk.

## FAQ

**Is BMI accurate for athletes?**
Not always. Muscle is dense, so muscular people can have a high BMI with low body fat.

**Does BMI differ for men and women?**
The adult formula and categories are the same for both sexes.

**Can children use this calculator?**
No. Under 20 years, BMI must be compared with growth charts for age and sex.

**What is a healthy BMI?**
For most adults, 18.5 to 24.9.

**What formula does the BMI Calculator use?**
BMI = weight (kg) ÷ height (m)².

**Can I work backwards from the result?**
Yes. Type the result you want into Body mass index and the calculator finds the matching weight.


## Sources

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