BMI Calculator
Quick weight category check based on height and weight. Returns BMI score, category, and healthy weight range.
Body Mass Index (BMI)
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What BMI actually measures
BMI is a screening tool, not a diagnostic one. It uses height and weight to estimate whether your weight falls in a range associated with higher or lower metabolic risk. The calculation is simple: weight in kilograms divided by height in meters squared.
A BMI between 18.5 and 24.9 is associated with the lowest statistical risk of cardiovascular disease, diabetes, and all cause mortality. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. These bands are population statistics, not individual predictions.
What BMI gets wrong
BMI does not distinguish between fat and muscle. A heavily muscled athlete can register as overweight or obese on BMI while having very low body fat. Older adults can register as normal weight while having lost significant muscle and gained fat, a condition called sarcopenic obesity.
BMI also does not account for fat distribution. Visceral fat around the abdomen carries more health risk than subcutaneous fat around the hips and thighs, even at the same BMI. For this reason, BMI is best used alongside a waist circumference measurement and body fat percentage estimate.
When BMI is most useful
BMI shines as a quick population level screening tool. For most sedentary adults, it correlates well with body fat percentage and metabolic risk. It is also useful for tracking changes over time, since the math is the same every time.
For athletes, bodybuilders, pregnant women, older adults with muscle loss, and very tall or short individuals, BMI should be supplemented with body fat percentage or waist measurements for a more accurate picture.
Frequently asked questions
Quick answers to the most common questions about this calculator.
Is BMI accurate for muscular people?+
No. BMI does not distinguish muscle from fat. A bodybuilder at 12 percent body fat can register as obese on BMI. Use body fat percentage or waist measurements if you carry significant muscle mass.
What is a healthy BMI for older adults?+
Some research suggests a slightly higher BMI (23 to 27) is associated with better outcomes in adults over 65. Very low BMI in older adults is linked to frailty and bone loss. Talk to your doctor about your individual risk profile.
Does BMI work for teenagers?+
BMI for children and teens uses percentiles rather than fixed cutoffs. If you are under 18, ask your pediatrician to interpret your BMI using age-specific growth charts.