Adult BMI Calculator
Calculate Body Mass Index (BMI) for adults aged 18 and over from height and weight.
For adults aged 18 and over. This calculator provides general information and is not a diagnosis or medical advice.
Your BMI result
Your BMI result will appear here.
Category:
Healthy BMI range for adults: 18.5 to 24.9
BMI is a screening measure. It does not diagnose a health condition and does not directly measure body fat.
BMI is shown to one decimal place, and a result starting with ≈ has been rounded. A difference of a few tenths is not meaningful for health.
Adult BMI ranges
- UnderweightBelow 18.5Your result
- Healthy weight18.5 to 24.9Your result
- Overweight25.0 to 29.9Your result
- Obesity30.0 and aboveYour result
How we calculated this
BMI is calculated by dividing weight in kilograms by height in metres, squared. Feet, inches, stone and pounds are converted to metres and kilograms with exact factors first. The calculation is exact and only the display is rounded.
Adult BMI categories
These are the standard adult BMI ranges used by the NHS, the World Health Organization and the CDC. They are a screening guide and not a diagnosis, and they are not adjusted for muscle mass, body composition or ethnic background.
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 and above | Obesity |
Limitations
This calculator is for adults aged 18 and over. BMI is not suitable during pregnancy, for children and teenagers, or for anyone with an eating disorder or a condition that affects height.
BMI uses only weight and height. It does not directly measure body fat, and it cannot tell muscle from fat, so it can be misleading for people with a lot of muscle. It also says nothing about where fat is carried or about overall health, and health risk varies from person to person at the same BMI.
Some guidance uses different BMI thresholds for some population groups. For example, the NHS advises lower thresholds for adults from South Asian, Chinese, other Asian, Middle Eastern, Black African and African Caribbean backgrounds, because health risks can begin at a lower BMI. Numerila does not ask about ethnic background and applies the standard ranges to everyone. For any concern about your weight or health, speak to a qualified healthcare professional.
Privacy
Your height and weight stay in your browser. They are not sent anywhere or stored.
Related information
See Editorial & Calculation Standards for how this and other Numerila calculators are sourced and tested, and the Disclaimer for the full limitations of every health, financial and maths tool on the site.
What this result means
The category shown is a screening label from the standard adult BMI ranges. It is not a diagnosis, so read the limitations below for what it does not tell you.
Sources and review
- World Health Organization, obesity and overweight fact sheet: the BMI formula, and overweight at 25 or more and obesity at 30 or more for adults
- World Health Organization, Global Health Observatory: the adult underweight indicator, a BMI below 18.5
- NHS, BMI calculator for adults: adults aged 18 and over, who should not use it, and BMI not telling muscle from fat
- NHS, obesity: the ranges 25 to 29.9 and 30 or more, and lower thresholds for some ethnic backgrounds
- CDC, adult BMI categories: the four adult ranges, and BMI as a screening measure
Reviewed: 30 September 2026.