Free BMI calculator
BMI calculator
Your body mass index, your adult category and where you sit on the scale. Honest and simple.
Your BMI
–
Category
Enter height and weight
- Underweight < 18.5
- Healthy weight 18.5 – 24.9
- Overweight 25 – 29.9
- Obesity 30 +
Adult categories apply from age 20 and are the same for men and women.
Under 20: children and teens are assessed with BMI-for-age percentiles, not the adult cut-offs above. We do not guess a percentile.
Use the CDC Child and Teen BMI Calculator or the CDC growth charts for girls, or ask a doctor or school nurse.
For children under 2, growth is checked with weight-for-length charts instead of BMI.
Estimate only, not a diagnosis and not medical advice.
How it works
BMI is your weight in kilograms divided by your height in metres squared. In pounds and inches it is 703 × weight ÷ height². See the formula and an example.
The adult categories follow the WHO and CDC: see all BMI categories, or look yourself up in the BMI chart by height and weight.
For a steady number, weigh yourself on a bathroom scale at the same time of day, ideally in the morning.
Questions
What is a healthy BMI?
For adults aged 20 and over, a BMI from 18.5 to 24.9 is called healthy weight by the WHO and CDC. Under 18.5 is underweight, 25 to 29.9 overweight and 30 or more obesity.
Why is my child's BMI not given a category?
Children and teens (2 to 19) are assessed with BMI-for-age percentiles on sex-specific growth charts, not adult cut-offs. This site does not guess a percentile; use the CDC growth charts or ask your child's doctor.
Does BMI work for athletes?
Not well. BMI cannot tell muscle from fat, so very muscular people can have a high BMI without high body fat.
Is BMI different for men and women?
The adult categories are the same for both sexes. Sex matters for children and teens, who are compared with separate growth charts for boys and girls.