BMI Calculator
Work out your body mass index (BMI) and the healthy weight range for your height.
About this tool
Enter your weight and height to get your BMI and its category on the World Health Organization scale for adults. BMI is a screening number, not a diagnosis: it does not measure body fat directly and is not used the same way for children, pregnant women or very muscular people.
Body mass index (BMI) compares your weight with your height and is a quick way to see whether your weight falls in the range usually linked with good health. Enter your height and weight in metric or imperial units to get your BMI, its category and the weight range that would give a BMI of 18.5 to 24.9 at your height. It runs in your browser.
How to use the BMI Calculator
- Choose metric or imperial units.
- Enter your weight and your height.
- Read your BMI and its category.
- Check the healthy weight range for your height underneath.
70 kg and 175 cm
BMI is weight in kilograms divided by height in metres squared. 1.75 × 1.75 = 3.0625, and 70 ÷ 3.0625 = 22.9, which is in the healthy weight range of 18.5 to 24.9. At 1.75 m that range runs from about 56.7 kg (18.5 × 3.0625) to 76.3 kg (24.9 × 3.0625).
What the categories mean
For adults, the World Health Organization uses these bands: below 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight and 30 or more is obesity. BMI is useful as a first check across large groups but it has limits for individuals. It cannot tell muscle from fat, so athletes can score as overweight, and it does not show where fat is carried; waist size adds useful information. Some health services use lower cut-offs for people of South Asian, Chinese and Black African or Caribbean heritage. BMI for children and teenagers is judged against age and sex percentiles instead. Talk to a doctor or nurse about what your number means for you.
Frequently asked questions
What is a healthy BMI?
For most adults, 18.5 to 24.9. Below 18.5 is underweight, 25 to 29.9 is overweight and 30 or above is obesity.
How is BMI calculated?
Weight in kilograms divided by height in metres squared. In imperial units it is weight in pounds × 703 divided by height in inches squared.
Is BMI accurate for athletes?
Not very. Muscle is heavier than fat, so a muscular person can have a high BMI with little body fat. Waist measurement or body-fat tests give a better picture.
Can I use this for children?
No. Children’s BMI is compared with growth charts for their age and sex. Ask a health professional or use a child BMI chart.