BMI Calculator (Body Mass Index)
Check your body mass index and see where it falls on the standard WHO scale — underweight, normal, overweight or obese. Works in metric (cm/kg) or imperial (inches/lbs), and also shows the healthy weight range for your height.
How to use this calculator
- Choose Metric (cm and kg) or Imperial (inches and lbs).
- Enter your height — for imperial, convert feet to total inches (5 ft 7 in = 67 inches).
- Enter your weight and press Calculate.
- Read your BMI, its category, and the healthy weight range for your height.
Formula used
The World Health Organization categories for adults: under 18.5 = underweight, 18.5–24.9 = normal, 25–29.9 = overweight, 30+ = obese. The same thresholds apply to men and women.
Example calculation
Height 170 cm, weight 70 kg: BMI = 70 ÷ (1.70)² = 70 ÷ 2.89 = 24.2 — within the normal range.
The healthy weight range for 170 cm is 18.5 × 2.89 to 24.9 × 2.89 = 53.5 – 72.0 kg.
What is BMI?
Body Mass Index is a simple screening number that relates your weight to your height. It was designed for studying populations, and it remains the most widely used quick check for weight-related health risk because it needs only two measurements.
Its main limitation: BMI can't tell muscle from fat. Athletes with high muscle mass often read "overweight" while being very lean, and older adults can have a normal BMI while carrying excess fat. That's why doctors pair BMI with waist circumference, body fat percentage and other markers. Treat your BMI as a starting point for a conversation, not a verdict.
Why use this calculator?
- Get an instant, standardized reference point used by doctors and health guidelines worldwide.
- See the healthy weight range for your height — a more actionable number than the BMI itself.
- Track changes over time: the trend in your BMI matters more than any single reading.
Frequently asked questions
What is a good BMI for my age?
For all adults 20 and older, the standard healthy range is 18.5–24.9 regardless of age or sex. For children and teens, BMI is assessed using age- and sex-specific percentile charts instead of fixed cutoffs.
Is BMI accurate for muscular people?
Not very. Muscle is denser than fat, so muscular people often register as overweight despite low body fat. If you train regularly, a body fat percentage measurement gives a much better picture.
How can I calculate BMI by hand?
Metric: divide your weight in kilograms by your height in meters squared — 70 ÷ (1.7 × 1.7) = 24.2. Imperial: multiply your weight in pounds by 703, then divide by your height in inches squared.
Does BMI differ for men and women?
The formula and categories are identical for both. Women naturally carry more body fat at the same BMI, which is one more reason BMI is a rough screen rather than a precise body-composition measure.
What should I do if my BMI is outside the normal range?
Don't panic over one number. Look at it alongside waist size, energy levels, fitness and diet — and if it's significantly high or low, discuss it with a doctor, who can assess what it actually means for your health.