Calculate your body mass index (BMI) from your height and weight. Choose metric or US units, type your numbers and see your BMI, your weight category and the weight range that matches a healthy BMI for your height.
All Free ToolsCalculatorsAge CalculatorPercentage Calculator
For adults aged 20 and over. BMI is a screening number, not a diagnosis. Calculated in your browser.
What Is BMI?
Body mass index, or BMI, is a number that compares your weight with your height. It is used as a quick screening tool to see whether an adult is in a lower, healthy or higher weight range. It is simple to work out, which is why doctors and health websites use it widely.
How Is BMI Calculated?
BMI is your weight in kilograms divided by your height in metres squared. For example, a person who weighs 70 kg and is 1.70 m tall has a BMI of 70 / (1.70 x 1.70) = 24.2. With US units the formula is weight in pounds divided by height in inches squared, multiplied by 703. This calculator does the work for you.
BMI Categories for Adults
- Under 18.5: underweight.
- 18.5 to 24.9: healthy weight.
- 25 to 29.9: overweight.
- 30 or more: obesity.
These are the ranges used by the World Health Organization for adults. The colored bar above the result shows where your number sits.
What BMI Cannot Tell You
- BMI does not measure body fat. A muscular athlete can have a high BMI and still be healthy.
- It does not show where fat is stored, and fat around the waist carries more risk than fat on the hips or legs.
- It may be less accurate for older adults, pregnant women and people who are very tall or very short.
- Children and teenagers are measured differently, using growth charts for their age.
Use your result as a starting point for a conversation, not as a diagnosis. If you are worried about your weight or your health, speak with a doctor or another qualified health professional.
Frequently Asked Questions
What is a good BMI?
For most adults a BMI between 18.5 and 24.9 is considered a healthy weight. The result box also shows the weight range that matches this BMI for your height.
Is this BMI calculator free?
Yes. It is free to use, with no sign-up. Your numbers stay in your browser and are not sent to us.
Is BMI accurate?
It is a useful screening number but not a perfect one, because it ignores muscle, bone and where fat is stored. A doctor can look at the full picture.
Can I use this for my child?
No. Children and teenagers need age and sex specific growth charts. Ask your doctor or nurse.
How do I convert pounds to kilograms?
Multiply the pounds by 0.4536. Or switch the units to US units and type your weight in pounds.
More Free Tools
Try the age calculator, the percentage calculator, the date difference calculator, see all calculators, or browse all free online tools.