BMI Calculator
Enter your weight and height in stones and feet or in metric units and get your BMI instantly. The calculation runs in your browser: nothing is sent or stored.
Enter a weight and a height to see your result.
Results are estimates. Solvemis accepts no responsibility for the results obtained or for how they are used. Always double-check the result and talk to a qualified professional before making decisions.
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How it works
How to use it
- Choose stones and pounds or kilograms, and enter your weight.
- Enter your height in feet and inches or in centimetres.
- Your BMI and its category appear instantly, without pressing any button.
How it is calculated
Weight in kilograms is divided by the square of height in metres; stones, pounds, feet and inches are converted first (1 stone = 14 lb = 6.35029318 kg, 1 inch = 2.54 cm). The categories follow the ranges used by the NHS and the World Health Organization for adults: underweight below 18.5, healthy weight up to 24.9, overweight up to 29.9 and obesity from 30.
BMI = weight (kg) ÷ height (m)²
Sources
- Calculate your body mass index (BMI) for adults — NHS
- Obesity and overweight (fact sheet) — World Health Organization
About this calculator
What body mass index measures
Body mass index relates your weight to your height: weight in kilograms divided by height in metres squared. At 11 stone (69.85 kg) and 5 ft 9 in (1.75 m), that gives 69.85 ÷ (1.7526 × 1.7526) = 22.7.
The ranges
| BMI | Category |
|---|---|
| below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obesity |
For people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family backgrounds, the NHS uses lower thresholds: 23 or more is overweight and 27.5 or more is obese.
The limits of BMI
BMI is quick and comparable, but it doesn’t know what your weight is made of. It doesn’t tell muscle from fat and says nothing about where that fat sits — and visceral fat, around the abdominal organs, matters far more metabolically than fat under the skin.
In practice, someone with a lot of muscle can be classed as overweight while having a low body fat percentage. Waist measurement is a useful extra check you can do at home: the NHS suggests your waist should be less than half your height.
This result is a guide, not a diagnosis. If you have doubts about your health, your GP is the right person to ask.
Frequently asked questions
What BMI is considered healthy?
For most adults, the NHS puts a healthy weight between 18.5 and 24.9. Below 18.5 is underweight, 25 to 29.9 is overweight and 30 or more is obesity.
Does BMI work the same for everyone?
Not quite. The NHS notes that people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family backgrounds have a higher health risk at a lower BMI: for them, 23 or more is considered overweight and 27.5 or more obese.
Updated 1 October 2026
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