BMI Calculator
Body Mass Index (BMI) compares your weight to your height. It is a quick, free screening number used by doctors and public-health agencies worldwide to sort adults into weight categories. Enter your height and weight below to see your BMI and what it means.
How BMI is calculated
BMI is your weight in kilograms divided by the square of your height in meters. With pounds and inches, the same result comes from multiplying by 703:
BMI = weight (kg) ÷ height (m)²
BMI = 703 × weight (lb) ÷ height (in)²
The calculator converts everything to metric internally, computes BMI, and rounds it to one decimal place. The category is assigned from that same rounded number, so a BMI of 24.95 — displayed as 25.0 — is shown as Overweight, matching what you see.
Adult BMI categories
The CDC and NIH use these categories for adults aged 20 and older, regardless of sex or age:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy (normal) weight |
| 25.0 to 29.9 | Overweight |
| 30.0 and above | Obesity (class 1: 30–34.9, class 2: 35–39.9, class 3: 40+) |
Adults vs. children and teens
These cutoffs are for adults only. For children and teens aged 2 to 19, BMI is calculated the same way but interpreted as a percentile compared with other children of the same age and sex, using CDC growth charts. A BMI of 22 might be healthy for an adult but high for a 10-year-old. If you are checking a child's BMI, use the CDC Child and Teen BMI Calculator and discuss the result with a pediatrician.
What BMI can and cannot tell you
At the population level, higher BMI is associated with higher risk of type 2 diabetes, high blood pressure, heart disease and some cancers, while very low BMI is linked with nutritional deficiency and bone loss. That is why BMI is useful for screening. But BMI does not measure body fat directly, and it cannot tell muscle from fat or show where fat is stored. Pair it with waist measurements — see our Waist-to-Hip Ratio Calculator — or a body fat estimate for a fuller picture.
BMI and waist size together
The NIH suggests that adults with a BMI of 25–34.9 also check waist circumference: a waist above 40 inches (102 cm) for men or 35 inches (88 cm) for women indicates higher risk of type 2 diabetes and heart disease at the same BMI. Combining both measures gives a better screening picture than either alone.
Healthy weight ranges by height
| Height | BMI 18.5–24.9 weight range |
|---|---|
| 5′0″ (152 cm) | 95–127 lb (43–58 kg) |
| 5′4″ (163 cm) | 108–145 lb (49–66 kg) |
| 5′8″ (173 cm) | 122–164 lb (55–74 kg) |
| 6′0″ (183 cm) | 136–184 lb (62–83 kg) |
Worked examples
Example 1: 160 lb, 5′9″
Height 69 in. BMI = 703 × 160 ÷ 69² = 112,480 ÷ 4,761 = 23.6 → Healthy weight.
Example 2: 60 kg, 165 cm
Height 1.65 m. BMI = 60 ÷ 1.65² = 60 ÷ 2.7225 = 22.0 → Healthy weight.
Example 3: 230 lb, 5′10″
Height 70 in. BMI = 703 × 230 ÷ 4,900 = 33.0 → Obesity (class 1). A doctor may suggest further checks such as waist circumference, blood pressure and blood sugar.
Limitations
- Muscular people (athletes, people who lift weights) can have a high BMI with low body fat.
- Older adults may have a "normal" BMI with low muscle and higher fat.
- Risk at a given BMI differs between ethnic groups; for example, some Asian populations show higher risk at lower BMIs.
- BMI ignores fat distribution; abdominal fat carries more risk than fat on the hips.
Who should not rely on this calculator
Do not use adult categories for children or teens under 20, or during pregnancy. People with high muscle mass, amputations, or conditions that change body composition or fluid balance should interpret BMI with a clinician.
Frequently asked questions
What is a healthy BMI for adults?
For adults 20 and older, a BMI of 18.5 to 24.9 is classed as healthy weight by the CDC and NIH.
Is BMI different for men and women?
No. The adult formula and categories are the same for men and women, although women typically carry more body fat than men at the same BMI.
Can I use this BMI calculator for my child?
No. Children and teens need age- and sex-specific BMI percentiles. Use the CDC Child and Teen BMI Calculator and talk to your pediatrician.
Why does my BMI say overweight when I am muscular?
BMI only uses height and weight, so it cannot tell muscle from fat. A body fat estimate or waist measurement can help.
Why is my category based on the rounded BMI?
So the category always matches the number shown. A BMI of 24.95 displays as 25.0, which falls in the Overweight range.
Is BMI a diagnosis?
No. BMI is a screening tool. A healthcare provider considers it alongside other measures such as waist size, blood pressure and lab results.
Sources
- Centers for Disease Control and Prevention. Adult BMI Categories. https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html
- Centers for Disease Control and Prevention. BMI Calculator for Child and Teen. https://www.cdc.gov/bmi/child-teen-calculator/index.html
- National Heart, Lung, and Blood Institute (NIH). Calculate Your Body Mass Index. https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm