BMI Calculator
Calculate Body Mass Index (BMI) from height and weight, in metric or imperial units, with weight category.
About the BMI Calculator
Body Mass Index is the most widely used screening measure linking weight to height, giving a quick sense of whether someone falls into an underweight, healthy, overweight, or obese range. This calculator works in both metric and imperial units and returns your BMI along with its standard category.
How It Works
The calculator converts your height and weight to metric units if needed, then divides weight in kilograms by height in meters squared to get BMI. It compares that number against the standard World Health Organization thresholds to assign a weight category.
BMI = Weight (kg) / [Height (m)]².
Worked example
Scenario: An adult who weighs 70 kg and is 175 cm tall (about 154 lb and 5 ft 9 in).
- Convert height to metres: 175 cm = 1.75 m.
- Square it: 1.75 × 1.75 = 3.0625.
- BMI = 70 ÷ 3.0625 = 22.9.
- For 1.75 m, a BMI of 18.5–24.9 corresponds to about 56.7–76.3 kg.
Result: A BMI of 22.9, in the healthy-weight range for adults.
Healthy-weight range by height
For adults, the WHO healthy range is a BMI of 18.5 to 24.9. The table converts that range into weights for common heights so you can read it without doing the arithmetic. The last column shows a BMI of 23 — the point at which WHO's 2004 expert consultation suggested many Asian populations may already face higher health risk, which is why some countries use lower cut-offs.
| Height (cm) | Height (ft/in) | Healthy range (kg) | Healthy range (lb) | BMI 23 (kg) |
|---|---|---|---|---|
| 150 | 4 ft 11 in | 41.6 – 56.0 | 92 – 124 | 51.8 |
| 155 | 5 ft 1 in | 44.4 – 59.8 | 98 – 132 | 55.3 |
| 160 | 5 ft 3 in | 47.4 – 63.7 | 104 – 141 | 58.9 |
| 165 | 5 ft 5 in | 50.4 – 67.8 | 111 – 149 | 62.6 |
| 170 | 5 ft 7 in | 53.5 – 72.0 | 118 – 159 | 66.5 |
| 175 | 5 ft 9 in | 56.7 – 76.3 | 125 – 168 | 70.4 |
| 180 | 5 ft 11 in | 59.9 – 80.7 | 132 – 178 | 74.5 |
| 185 | 6 ft 1 in | 63.3 – 85.2 | 140 – 188 | 78.7 |
| 190 | 6 ft 3 in | 66.8 – 89.9 | 147 – 198 | 83.0 |
BMI does not measure body fat directly. A muscular person can score as "overweight" with little fat, and an older adult can score as "healthy" while carrying more fat than the number suggests. Waist measurement or the body fat calculator adds context. BMI categories here apply to adults only; children and teenagers are assessed with age- and sex-specific percentiles. You can now enter height in feet and inches and weight in pounds — switch the units at the top of the calculator.
Tips and common mistakes
- In imperial mode, enter height in total inches: 5 ft 9 in = 69 in.
- BMI doesn't distinguish muscle from fat, so athletes can read as overweight.
- Adult categories don't apply to children and teens, who are assessed with age- and sex-specific percentiles.
- Waist circumference adds useful context: health risk rises above about 102 cm (40 in) for men and 88 cm (35 in) for women.
Assumptions & Limitations
- Uses the standard adult BMI thresholds: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30+ obese.
- Applies the same formula regardless of age or sex, consistent with the standard BMI definition.
- BMI does not distinguish muscle mass from fat mass, so very muscular individuals may show a higher BMI without excess body fat.
- Not designed for children, pregnant women, or elderly individuals, who need different assessment methods.
Evidence-based interpretation
For adults age 20 and older, the CDC classifies BMI below 18.5 as underweight, 18.5 to under 25 as healthy weight, 25 to under 30 as overweight, and 30 or higher as obesity. BMI is a screening measure, not a diagnosis, and should be interpreted alongside factors such as medical history, health behaviors, blood pressure, muscle mass, and laboratory findings.
BMI does not directly measure body fat. A muscular person can have a high BMI without having high body fat, while BMI can also miss differences in abdominal fat distribution. Children and teens require age- and sex-specific BMI percentiles rather than adult cutoffs.
Sources and review
Method: BMI = weight (kg) ÷ height (m)². Adult categories: below 18.5 underweight, 18.5–24.9 healthy weight, 25–29.9 overweight, 30 and above obesity.
Sources:
- World Health Organization (WHO), adult body mass index classification.
- U.S. Centers for Disease Control and Prevention (CDC), adult BMI categories.
Last reviewed: October 2026 by Faheem Ali, founder of CalculatorAnything. The method and examples are provided for transparency; results remain estimates and may contain errors.
Results are estimates for general information and screening, not a diagnosis or medical advice. Talk to a qualified healthcare professional before making health or diet decisions. Spotted an error? Tell us — see our editorial policy for how corrections are handled.