Fitness
BMI Calculator
Enter height and weight in metric or imperial to get your BMI and weight category.
How it works
BMI = weight (kg) ÷ height (m)². The NHS uses the same formula: under 18.5 is underweight, 18.5–24.9 is healthy, 25–29.9 is overweight, and 30+ is obese. For imperial, weight is converted to kg and height to metres before calculation.
Frequently asked questions
Is BMI an accurate measure of health?
BMI is a useful starting point but has limits. It doesn't account for muscle mass, bone density, age, sex or fat distribution. Athletes often score 'overweight' despite low body fat.
What is a healthy BMI?
The NHS considers 18.5–24.9 healthy for most adults. Different thresholds apply for some ethnic groups — South Asian adults, for example, may face higher health risks at lower BMI scores.
How often should I check my BMI?
BMI changes slowly. Checking monthly is usually enough unless you're tracking a specific fitness goal.