BMI Calculator
Work out your body mass index from your height and weight, and the healthy weight range for your height.
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cm
kg
Pick any unit for each, for example feet and inches with kilograms.
How your BMI is worked out
Your numbers, step by step. BMI = weight ÷ height².
- 1
Height in metres
175 cm → 1.75 m
- 2
Square it
1.75 × 1.75 = 3.06
- 3
Divide your weight by it
70 kg ÷ 3.06 = 22.9
- 4
Find your range
22.9 → Healthy weight
Read more: BMI ranges, a worked example and its limits
What BMI tells you
Body mass index compares your weight with your height. It's a quick screening measure used by doctors and health services, not a diagnosis.
BMI = weight (kg) ÷ height (m)²
| BMI | Range (WHO) |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25 – 29.9 | Overweight |
| 30 and above | Obesity |
Worked example
Someone 175 cm tall weighing 70 kg has a BMI of 70 ÷ 1.75² = 70 ÷ 3.0625 = 22.9, in the healthy range. For that height the healthy range is about 57 to 76 kg.
Its limits
- BMI doesn't separate muscle from fat, so very muscular people can show as overweight.
- For people of South Asian, Chinese and some other Asian backgrounds, health risks start at a lower BMI. Many health services use 23 and 27.5 as the thresholds instead of 25 and 30.
- It isn't meant for children, teenagers or pregnant women, who need age- or pregnancy-specific measures.
- Waist size adds useful information: a waist more than half your height is linked to higher health risk.
General information, not medical advice. Talk to a doctor about what your BMI means for you.