How BMI is calculated
BMI is calculated by dividing weight in kilograms by height in meters squared. The imperial version uses weight in pounds multiplied by 703, divided by height in inches squared. Both formulas produce the same result and are used by health organizations worldwide as a quick screening measure.
What the categories mean
A BMI under 18.5 is classed as underweight, 18.5 to 24.9 as a healthy weight range, 25 to 29.9 as overweight, and 30 or above as obese. BMI is a general screening tool, not a diagnosis — it doesn't account for muscle mass, bone density, or body composition, so athletes and very muscular individuals often score higher without added health risk. If you have concerns about your weight or health, a doctor can give guidance suited to your individual situation.
Frequently asked questions
Is BMI an accurate measure of health?
BMI is a useful general screening tool but has known limitations — it doesn't distinguish between muscle and fat, so very muscular people can show a higher BMI without added health risk. It's best used as a starting point, not a diagnosis.
Does this calculator adjust for age or gender?
No. The standard BMI formula used here is the same for all adults regardless of age or gender. Some health providers use different reference ranges for children and teenagers, which this tool does not calculate.
What should I do if my BMI is outside the healthy range?
A single BMI number shouldn't be treated as a verdict on your health. If you have concerns, a doctor can look at the full picture — body composition, medical history, and lifestyle — and give guidance suited to you specifically.
Can I switch between metric and imperial units mid-calculation?
Yes, use the tabs above the input fields to switch between kg/cm and lb/ft-in at any time; your BMI will recalculate immediately using whichever unit set is active.