BMI Calculator (Adults: Men & Women)

How to calculate BMI (the BMI formula)

BMI = weight (kg) ÷ height (m)². In US units: BMI = 703 × weight (lb) ÷ height (in)². Example: 70 kg and 1.75 m → 70 ÷ 3.06 = 22.9. The calculator above does the conversion for you; if you do it by hand, square the height first, then divide.

BMI chart for adults: men and women

BMI	Category (WHO / CDC)
below 18.5	underweight
18.5 – 24.9	healthy weight
25.0 – 29.9	overweight
30.0 – 34.9	obesity class 1
35.0 – 39.9	obesity class 2
40.0 and above	obesity class 3

The same cut-offs are used for adult men and women. For children and teens BMI is read against age-and-sex percentiles instead, so this calculator is for adults only.

What is a normal BMI range?

For adults, 18.5–24.9 is the range linked with the lowest risk of weight-related disease in large population studies. Being slightly above it does not mean you are unhealthy: waist size, blood pressure, blood lipids, fitness and family history matter at least as much. If your BMI is 25 or higher, the waist-to-hip ratio calculator adds the second piece of the picture — where the weight sits.

BMI vs ideal body weight

BMI gives a range; “ideal weight” formulas give a single number from height alone. Neither knows how much of your weight is muscle. Use BMI to see whether you are inside the healthy band, and the ideal weight calculator only as a rough reference point, not a target.

What BMI does not measure

BMI cannot tell fat from muscle. A muscular person can score “overweight” with low body fat, and an older adult can score “healthy” while carrying too little muscle. Pregnancy, very short or very tall stature, and some ethnic backgrounds also shift the risk at a given BMI. When BMI and your mirror disagree, measure body fat or waist instead.

Sources

• WHO, Obesity and overweight fact sheet (2025) — https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
• CDC, Adult BMI Calculator — https://www.cdc.gov/bmi/adult-calculator/index.html
• NHLBI, BMI table — https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmi_tbl.htm

This calculator is educational and not medical advice. If you have a health condition, are pregnant, or are under 18, ask a clinician before changing your diet.