A BMI calculator divides your weight in kilograms by your height in meters squared to give your body mass index (BMI), a screening number for adults. For adults 20 and older, the CDC classes a BMI of 18.5 to 24.9 as healthy weight, 25 to 29.9 as overweight and 30 or more as obesity. For example, a person who is 5 ft 10 in and weighs 200 lb has a BMI of 28.7.
BMI is a screening tool, not a diagnosis.
On this page
How to use the BMI calculator
- Choose metric (kg and cm) or US units (lb, feet and inches).
- Enter your weight and height. Age and sex are optional and do not change the adult result.
- Read your BMI and its adult category.
This BMI calculator uses adult cutoffs. For anyone aged 2 to 19, use the CDC child and teen BMI calculator, which compares BMI with growth charts for age and sex.
What is the BMI formula?
- Metric: BMI = weight (kg) ÷ height (m)2
- US units: BMI = 703 × weight (lb) ÷ height (in)2
The 703 factor converts pounds and inches into the metric result. Height must be squared: a common mistake is dividing by height once.
BMI calculator worked examples
| Height | Weight | Calculation | BMI | Category |
|---|---|---|---|---|
| 175 cm | 70 kg | 70 ÷ 1.752 | 22.9 | Healthy weight |
| 5 ft 4 in (64 in) | 120 lb | 703 × 120 ÷ 642 | 20.6 | Healthy weight |
| 5 ft 5 in (65 in) | 160 lb | 703 × 160 ÷ 652 | 26.6 | Overweight |
| 5 ft 10 in (70 in) | 200 lb | 703 × 200 ÷ 702 | 28.7 | Overweight |
Adult BMI categories (CDC)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Class 1 obesity |
| 35.0 to 39.9 | Class 2 obesity |
| 40.0 or higher | Class 3 obesity |
The same cutoffs apply to adult men and women aged 20 and older.
Healthy weight range for your height
The weights below correspond to a BMI of 18.5 to 24.9:
| Height | Healthy weight range |
|---|---|
| 5 ft 0 in (152 cm) | 95 to 127 lb (43 to 58 kg) |
| 5 ft 4 in (163 cm) | 108 to 145 lb (49 to 66 kg) |
| 5 ft 8 in (173 cm) | 122 to 164 lb (55 to 74 kg) |
| 6 ft 0 in (183 cm) | 136 to 184 lb (62 to 83 kg) |
| 6 ft 4 in (193 cm) | 152 to 205 lb (69 to 93 kg) |
For a target weight based on other formulas, see the ideal weight calculator.
BMI and ethnicity
The NHS notes that people from Asian, Black African, African-Caribbean and Middle Eastern backgrounds have a higher risk of health problems at a lower BMI, so a result near the top of the healthy range may deserve more attention. Waist measurement adds useful information for everyone, because BMI does not show where fat is stored.
Children and teens
The bmi calculator uses adult cutoffs. For ages 2 to 19, BMI is compared with CDC growth charts for the same age and sex, and the result is a percentile: under the 5th is underweight, the 5th to under the 85th is healthy weight, the 85th to under the 95th is overweight, and the 95th or above is obesity. Use the CDC’s child and teen BMI tool for those ages.
Limits of BMI
- It does not distinguish muscle from fat, so athletes can score high.
- It does not show where fat is stored. Waist size adds that information: NHLBI treats a waist over 40 in (102 cm) for men or 35 in (88 cm) for non-pregnant women as higher risk.
- Risk at a given BMI differs across ethnic groups; WHO has suggested lower action points for many Asian populations.
- It is not used during pregnancy.
For a fuller picture, pair BMI with the body fat calculator and read what BMI means and its limits. To plan calorie changes, use the calorie calculator.
For a simple yes or no on BMI 25 or higher, see the overweight calculator.
This calculator is for education. Talk to a health professional about your weight and health.
BMI in pounds and inches
If you know your weight in pounds and height in inches, the BMI calculator uses the same formula with a conversion factor: BMI = 703 × weight in pounds ÷ height in inches squared. A person who weighs 180 pounds and stands 5 feet 10 inches (70 inches) has a BMI of 703 × 180 ÷ 4,900 = 25.8, just into the overweight range. The 703 comes from converting pounds to kilograms and inches to meters, so either set of units gives the same answer.
Related converters and calculators
Related tools:
- Body fat calculator: fat vs muscle
- Ideal weight calculator: target weight
- Calorie calculator: daily calories
- Overweight calculator: BMI 25 or higher
- Healthy weight calculator: range for your height
Want this BMI calculator on your own health or fitness blog? It is included in our WordPress calculator plugin along with BMR, calorie and body fat tools.
Sources
CDC: Adult BMI categories; CDC: Child and teen BMI calculator; NHLBI (NIH): Assessing your weight and health risk; NHS: Obesity.
Questions about this calculator
What is a healthy BMI?
For adults, the CDC classes a BMI of 18.5 to 24.9 as healthy weight.
How do I calculate BMI in pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. For 160 lb at 65 in: 703 × 160 ÷ 4,225 ≈ 26.6.
Is BMI different for men and women?
The adult categories are the same for both. Women tend to have more body fat than men at the same BMI.
Can I use this BMI calculator for children?
No. Children and teens need BMI-for-age percentiles from CDC growth charts.
What BMI is considered obese?
For adults, 30.0 or higher. The CDC splits it into Class 1 (30 to 34.9), Class 2 (35 to 39.9) and Class 3 (40 or higher).
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
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