About the BMI Calculator
Body mass index (BMI) is your weight divided by the square of your height. It is the standard quick screen for underweight, overweight and obesity in adults and is used by the WHO, the CDC and the NHS. This calculator uses the WHO adult categories: below 18.5 underweight, 18.5โ24.9 healthy weight, 25โ29.9 overweight and 30 or more obesity.
Results update as you type. The gauge shows where you sit, and the calculator also tells you which weights fall in the healthy range for your height.
How to use
- Choose ft ยท lb or cm ยท kg, then enter your height and weight.
- Read your BMI, its category and your position on the colored gauge.
- Check the healthy weight range for your height and how much you would need to gain or lose to reach it.
BMI formula and WHO categories
BMI = weight (kg) รท height (m)ยฒ, or in US units BMI = 703 ร weight (lb) รท height (in)ยฒ. For example, 5 ft 7 in (67 in) and 150 lb gives 703 ร 150 รท 67ยฒ = 23.5.
| Category | BMI (kg/mยฒ) |
|---|---|
| Underweight | below 18.5 |
| Healthy weight | 18.5 โ 24.9 |
| Overweight | 25 โ 29.9 |
| Obesity class I | 30 โ 34.9 |
| Obesity class II | 35 โ 39.9 |
| Obesity class III (severe) | 40 or more |
For people of South Asian, Chinese, other Asian, Black African or African-Caribbean background, health risks start at a lower BMI, and some guidelines (for example NICE in the UK) use 23 and 27.5 as action points.
Limits of BMI and what to check as well
- Muscular people can have a high BMI with little body fat.
- Adult categories do not apply to children and teens; they use BMI-for-age percentiles. They also donโt fit well during pregnancy or in older adults.
- Waist circumference adds information about belly fat: a waist above 40 in (102 cm) for men or 35 in (88 cm) for women signals higher risk.
FAQ
What is a healthy weight for my height?
Any weight that puts your BMI between 18.5 and 24.9. At 5 ft 7 in that is roughly 118โ159 lb. The calculator shows the exact range for your height.
Is a BMI of 25 overweight?
Yes. Under WHO and CDC definitions, a BMI from 25 to 29.9 is overweight and 30 or more is obesity.
Can I use this BMI calculator for children?
No. For anyone under 20 (CDC) or 18, BMI has to be compared with age- and sex-specific growth charts. The categories here are for adults only.
Is BMI a medical diagnosis?
No. BMI is a simple screening number. A doctor will look at it together with waist size, blood pressure, blood tests and your history. Talk to a health professional if you are concerned about your weight.