BMI Calculator
Calculate BMI from height and weight in metric (cm/kg) or imperial (ft/lbs). See your category, healthy weight range, and visual indicator. No signup.
infoBMI Categories
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BMI is a screening tool, not a diagnostic measure. It may not be accurate for athletes, elderly, or pregnant women. Consult a healthcare provider for a complete assessment.
What is the BMI Calculator?
Body Mass Index is a single number that estimates whether your weight falls in a healthy range for your height. It comes from a simple formula (weight in kilograms divided by height in meters squared) and lands you in one of four WHO categories. BMI ignores muscle mass and fat distribution, so it's a screening number, not a diagnosis.
How to use the BMI Calculator
- 1
Pick metric or imperial
Tap Metric for cm/kg or Imperial for ft/lbs. The form swaps to match.
- 2
Enter your height
Standing height, measured without shoes, gives the most consistent reading.
- 3
Enter your weight
Weigh yourself in light clothing for a stable number across days.
- 4
Read the result and category
Your BMI appears with a color-coded category and the weight range that would put you in the Normal band for your height.
Frequently Asked Questions
How is BMI calculated?
BMI = weight in kilograms divided by height in meters squared. So 80 kg at 1.80 m gives 80 / (1.80 × 1.80) = 24.7. Imperial inputs get converted internally before the formula runs, so the result matches whichever unit system you started from.
What are the BMI categories?
WHO standard cuts: under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, 30 and above is obese. Class II and III obesity start at 35 and 40 respectively, but the calculator collapses those into the obese band.
Is BMI accurate for everyone?
It's a population-level screening number, not a body composition test. Athletes with high muscle mass often score in the overweight range despite low body fat, and the elderly tend to score lower than their actual fat percentage. Pair BMI with waist measurement or a body composition scan for a fuller picture.