BMI Calculator
For adults 20 and older. Uses CDC's formula and adult BMI categories.
Enter your height, weight and age to see your BMI.
What your BMI result means
BMI is a measure of weight relative to height [1]. For adults, BMI categories are underweight, healthy weight, overweight, and obesity. Obesity is further subdivided into three classes [2]. CDC says these categories are based on a person's BMI regardless of age, sex, or race [2]. BMI is a screening measure and is not intended to diagnose disease or illness [3]. If you have questions about your BMI, talk with your health care provider [2].
Adult BMI categories
BMI categories for adults 20 and older [2]:
| BMI category | BMI range (kg/m2) |
|---|---|
| Underweight | Less than 18.5 |
| Healthy Weight | 18.5 to less than 25 |
| Overweight | 25 to less than 30 |
| Obesity | 30 or greater |
| Class 1 Obesity | 30 to less than 35 |
| Class 2 Obesity | 35 to less than 40 |
| Class 3 Obesity (Severe Obesity) | 40 or greater |
Example: an adult who is 5 feet 9 inches tall
CDC's example for an adult who is 5 feet 9 inches tall: 124 pounds or less is underweight, 125 to 168 pounds is healthy weight, 169 to 202 pounds is overweight, and 203 pounds or more is obesity [2].
What BMI doesn't tell you
BMI does not directly measure body fat, and it does not distinguish between fat, muscle, and bone mass [1]. BMI does not indicate what types of fat people have. BMI also does not indicate where in the body that people carry fat [1]. CDC says BMI is one potential health indicator and should be considered with other factors when assessing an individual's health [3]. These factors may include a patient's medical history, health behaviors, physical exam findings, and laboratory findings [3]. The National Heart, Lung, and Blood Institute (part of NIH) says BMI is "based on height and weight but doesn't take into account your muscle mass, bone density, or body composition" [4].
In the UK, the NHS says "people from an Asian, Black African, African-Caribbean or Middle Eastern ethnic background have a higher chance of developing health problems at a lower BMI" [5].
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Who shouldn't use this calculator
This calculator is for adults 20 and older [3]. For children and teens aged 2 through 19 years, use CDC's Child and Teen BMI Calculator [1][6].
This calculator is not designed for use during pregnancy.
In the UK, the NHS says you should not use its adult BMI tool if you: "have been diagnosed with an eating disorder, or think you may have one"; "have a condition that affects your height" [5].
How BMI is calculated
Metric: weight in kilograms divided by height in meters squared [7]. US: weight in pounds divided by height in inches squared, multiplied by 703 [7].
With height in centimeters, divide weight in kilograms by height in centimeters squared and multiply by 10,000 [7].
Worked examples
CDC's example: an adult who is 5 feet 8 inches tall and weighs 200 pounds has a BMI of 30.4. This BMI falls into the obesity category, defined as a BMI of 30.0 or higher [8].
The NHS example: an adult who weighs 70 kg and is 1.70 m tall has a BMI of 70 / (1.70 x 1.70) = 70 / 2.89 = 24.22, shown as 24.2 [5].
We round your BMI to one decimal place.
Adult BMI chart
Find your height, then read across to see the weight range for each CDC adult BMI category. The weights are calculated from CDC's adult BMI ranges [2] and rounded to whole pounds or kilograms.
Frequently asked questions
What is BMI?
BMI is a measure of weight relative to height [1]. It is a calculated measure of a person's body weight (in kilograms) divided by the square of their height (in meters) [1].
What is a healthy BMI for adults?
For adults 20 and older, CDC's Healthy Weight category is a BMI of 18.5 to less than 25 [2].
Is BMI different for men and women?
To interpret BMI values for adults 20 and older, use standard BMI categories regardless of age, sex, or race [8].
Can I use this for my child?
No. Because children and teens are growing, their BMI values are expressed relative to others of the same sex and age. These values are called BMI-for-age percentiles [9]. For children and teens 2 through 19, CDC's Child and Teen BMI Calculator reports BMI, BMI percentile, and BMI category [6].
How accurate is BMI?
CDC says BMI is a quick, low-cost, and reliable screening measure for underweight, overweight, or obesity [1]. For most people, BMI is a good indicator of whether they have too much or too little body fat [8]. However, BMI is not a direct measure of body fat [8].
Why does it ask if I'm pregnant?
This calculator is not designed for use during pregnancy. CDC has guidance on weight gain during pregnancy [10].
Why does it ask my age?
BMI is interpreted differently for children and adults [8]. This calculator gives a result only for adults 20 and older. For anyone younger, it shows a link to CDC's Child and Teen BMI Calculator instead.
Why do kg and lb give slightly different results?
The US formula multiplies by 703 [7]. Converting between units and rounding to one decimal place can make the same measurements differ by 0.1. Near the edge of a category, that can change the category shown.
Sources and how we check this tool
Last checked against CDC: 24 Oct 2026
This calculator uses CDC's formulas [7] and CDC's adult BMI categories for adults 20 and older [2]. It places your result in a category using your BMI rounded to one decimal place.
We re-check our sources every 6 months and whenever a source updates.
- Centers for Disease Control and Prevention (CDC). About Body Mass Index (BMI). Dec. 16, 2025. https://www.cdc.gov/bmi/about/index.html
- Centers for Disease Control and Prevention (CDC). Adult BMI Categories. March 19, 2024. https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html
- Centers for Disease Control and Prevention (CDC). Adult BMI Calculator. June 26, 2024. https://www.cdc.gov/bmi/adult-calculator/index.html
- National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health. Calculate Your BMI. https://www.nhlbi.nih.gov/calculate-your-bmi
- NHS. Calculate your body mass index (BMI) for adults. Page last reviewed 28 November 2023. https://www.nhs.uk/health-assessment-tools/calculate-your-body-mass-index/calculate-bmi-for-adults
- Centers for Disease Control and Prevention (CDC). Child and Teen BMI Calculator. June 26, 2024. https://www.cdc.gov/bmi/child-teen-calculator/index.html
- Centers for Disease Control and Prevention (CDC). Calculating BMI (Growth Chart Training). June 18, 2024. https://www.cdc.gov/growth-chart-training/hcp/using-bmi/calculating-bmi.html
- Centers for Disease Control and Prevention (CDC). BMI Frequently Asked Questions. https://www.cdc.gov/bmi/faq/index.html
- Centers for Disease Control and Prevention (CDC). Child and Teen BMI Categories. June 28, 2024. https://www.cdc.gov/bmi/child-teen-calculator/bmi-categories.html
- Centers for Disease Control and Prevention (CDC). Weight Gain During Pregnancy. May 15, 2024. https://www.cdc.gov/maternal-infant-health/pregnancy-weight/index.html
This calculator is for general information and is not medical advice. It does not diagnose any condition. Talk with your health care provider about your health.