What is BMI?
Body mass index compares your weight with your height. It is a quick screening measure used to put body weight into context, rather than a direct measurement of body fat or fitness. The same standard adult calculation is used for men and women.
Use kilograms and centimetres, or switch to stone, pounds, feet and inches. Enter a recent weight and your height without shoes. The calculator converts imperial measurements before applying the formula.
Understanding your result
| Adult BMI | Standard category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to below 25 | Healthy weight |
| 25 to below 30 | Overweight |
| 30 or above | Obesity |
These categories describe a population screening tool. They do not establish your individual health, nutritional needs or suitability for medication. A clinician may also consider your waist measurement, symptoms, blood pressure, blood results and medical history.
When BMI needs more context
Someone with a lot of muscle can have a high BMI without carrying excess body fat. BMI may also miss differences in fat distribution. Health risks can occur at lower BMI levels in people from some ethnic backgrounds, including South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds.
The reference weight range shown in your result is calculated from a BMI of 18.5 to 24.9 at your height. It is a mathematical reference, not an instruction to reach a particular weight. If your result is below 18.5, talk through any concerns with a clinician before trying to change your weight.
Use the number to choose a useful next step
If your goal is to understand energy needs, try the TDEE calculator. If you want support with weight management, explore Heracles weight-loss care. Your BMI alone does not determine eligibility for treatment.
Questions about this calculator
Is this a BMI calculator for men?
Yes. It works for adults aged 18 and over. The standard BMI formula is the same for men and women; the interpretation still needs individual context.
Does muscle affect BMI?
Muscle adds body weight, so a muscular person can have a higher BMI. BMI does not separate muscle, fat and bone or measure fat distribution.
Can I enter stone and pounds?
Yes. Select UK imperial and enter stone plus the remaining pounds, then feet plus the remaining inches. Switching units converts measurements you have already entered.
Does my BMI tell me if I can get weight-loss treatment?
No. Treatment suitability requires a clinical assessment of your overall health, history and other relevant factors.