BMI calculator
Enter your weight and height to see your BMI, what category it falls in, and the healthy weight range for your height.
Categories: CDC and World Health Organization adult BMI cutoffsLast reviewed: October 9, 2026
The short answer
BMI is your weight in kilograms divided by your height in meters squared. For adults 20 and older, under 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight, and 30 or higher is obesity, split into classes 1, 2 and 3. Children and teens use BMI-for-age percentiles instead.
How it is calculated
BMI = weight (kg) ÷ height (m)²
From pounds and inches: BMI = weight (lb) ÷ height (in)² × 703 (the calculator converts exactly: 1 lb = 0.45359237 kg, 1 in = 2.54 cm).
Healthy weight for your height = 18.5 × height² to 24.9 × height².
Worked example
Mike is 5′9″ and weighs 180 lb.
- Height: 69 inches = 175.26 cm = 1.7526 m
- Weight: 180 lb = 81.6 kg
- BMI: 81.6 ÷ 1.7526² = 26.6
- 26.6 is between 25 and 29.9, so the category is overweight
- Healthy weight at 5′9″: 125 to 169 lb
Mike's BMI is 26.6. He is about 11 lb above the top of the healthy range.
Quick reference table
| Height | Pounds | Kilograms |
|---|---|---|
| 4′10″ (147 cm) | 89–119 lb | 40.2–54.0 kg |
| 5′0″ (152 cm) | 95–127 lb | 43.0–57.8 kg |
| 5′2″ (157 cm) | 101–136 lb | 45.9–61.8 kg |
| 5′4″ (163 cm) | 108–145 lb | 48.9–65.8 kg |
| 5′6″ (168 cm) | 115–154 lb | 52.0–70.0 kg |
| 5′8″ (173 cm) | 122–164 lb | 55.2–74.3 kg |
| 5′10″ (178 cm) | 129–174 lb | 58.5–78.7 kg |
| 6′0″ (183 cm) | 136–184 lb | 61.9–83.3 kg |
| 6′2″ (188 cm) | 144–194 lb | 65.4–88.0 kg |
| 6′4″ (193 cm) | 152–205 lb | 68.9–92.8 kg |
Special cases and common mistakes
- Adult categories (CDC): underweight below 18.5; healthy weight 18.5 to under 25; overweight 25 to under 30; obesity class 1 from 30, class 2 from 35, class 3 (severe obesity) at 40 and above. The WHO uses the same cutoffs and calls 25 to 29.9 "pre-obesity."
- Kids and teens (ages 2 to 19): the BMI number is calculated the same way but is compared with growth charts for age and sex. Obesity is a BMI at or above the 95th percentile. This calculator does not do that comparison, so it shows no category if you enter an age under 20.
- Athletes and muscular people: BMI cannot tell muscle from fat, so a lean, muscular person can land in the overweight or obesity range.
- Older adults: muscle tends to drop and fat to rise with age, so BMI can look normal while body fat is high. A study of U.S. adults over 60 found BMI poorly identified obesity in this group.
- Pregnancy: do not use an adult BMI calculator while pregnant; your provider tracks weight gain against your pre-pregnancy BMI.
- Eating disorders: if you have or think you may have an eating disorder, talk to a clinician rather than relying on a BMI number.
Frequently asked questions
How do I calculate BMI in pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. At 150 lb and 5′6″ (66 in): 150 × 703 ÷ 4,356 = 24.2.
What is a healthy BMI for women and men?
For adults 20 and older it is 18.5 to 24.9 for both women and men. The formula and categories are the same; sex only matters for children and teens, whose growth charts are separate for boys and girls.
Does age change my BMI category?
Not for adults; the same cutoffs apply from age 20 on. Under 20, BMI is read as a percentile for age and sex. For older adults the cutoffs stay the same, but BMI is a weaker sign of body fat.
Is BMI accurate?
It is a quick screening number, not a diagnosis. It does not measure body fat directly or show where fat is carried. Your doctor may add waist size and other checks.
What should I weigh for my height?
A BMI of 18.5 to 24.9 is the healthy range. At 5′6″ that is 115 to 154 lb; the table above covers 4′10″ to 6′4″.
Sources
- CDC: Adult BMI Categories (Last reviewed: October 9, 2026)
- CDC: About Body Mass Index (limitations; children and teens) (Last reviewed: October 9, 2026)
- WHO Regional Office for Europe: Nutrition for a healthy life (BMI definition and classification table) (Last reviewed: October 9, 2026)
- WHO: Obesity and overweight fact sheet (adult and child definitions) (Last reviewed: October 9, 2026)
- NHS: Calculate your BMI (who should not use an adult BMI calculator) (Last reviewed: October 9, 2026)
- NHS: Obesity diagnosis (muscle, and lower cut-offs for some ethnic groups) (Last reviewed: October 9, 2026)
- Batsis et al., Diagnostic accuracy of BMI to identify obesity in older adults, International Journal of Obesity (PMC) (Last reviewed: October 9, 2026)