Last updated: November 3, 2026
To calculate BMI, divide your weight in kilograms by your height in meters squared. In pounds and inches, divide weight by height squared and multiply by 703. For adults, a BMI of 18.5 to under 25 is a healthy weight, 25 to under 30 is overweight, and 30 or more is obesity.
Contents
- What is the BMI formula?
- How to calculate BMI step by step
- Adult BMI chart and categories
- Healthy weight range by height
- How to calculate BMI for women and men
- How to calculate BMI for kids and teens
- How to calculate BMI in Excel
- What BMI does not tell you
- Frequently asked questions
What is the BMI formula?
Body mass index (BMI) is a measure of body weight relative to height. The CDC gives three equivalent ways to calculate BMI by hand in its BMI frequently asked questions:
| Units | BMI formula | When to use it |
|---|---|---|
| Kilograms and meters | weight (kg) ÷ [height (m)]2 | The standard metric formula |
| Kilograms and centimeters | [weight (kg) ÷ height (cm) ÷ height (cm)] × 10,000 | When height is measured in centimeters |
| Pounds and inches | weight (lb) ÷ [height (in)]2 × 703 | U.S. customary units |
The factor of 703 converts pounds and inches into the metric units BMI is defined in, so both formulas give the same result.
How to calculate BMI step by step
How to calculate BMI in pounds and inches
- Convert your height to inches. For example, 5 feet 8 inches is 68 inches.
- Square your height: 68 × 68 = 4,624.
- Divide your weight in pounds by that number: 200 ÷ 4,624 = 0.04325.
- Multiply by 703: 0.04325 × 703 = 30.4.
- Round to one decimal place and compare the result with the BMI chart below.
This matches the CDC’s own example: an adult who is 5 feet 8 inches tall and weighs 200 pounds has a BMI of 30.4, which falls in the obesity category (CDC).
How to calculate BMI in kilograms and meters
- Write your height in meters. For example, 175 centimeters is 1.75 meters.
- Square your height: 1.75 × 1.75 = 3.0625.
- Divide your weight in kilograms by that number: 70 ÷ 3.0625 = 22.9.
A BMI of 22.9 falls in the healthy weight range for adults. For other unit changes, see our km to miles conversion guide.
Adult BMI chart and categories
For adults 20 and older, the CDC uses these adult BMI categories regardless of age, sex or race:
| 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 |
| Class 1 obesity | 30 to less than 35 |
| Class 2 obesity | 35 to less than 40 |
| Class 3 obesity (severe obesity) | 40 or greater |
The World Health Organization uses the same adult cut points: overweight is a BMI of 25 or more and obesity is a BMI of 30 or more.
Healthy weight range by height
The table below applies the U.S. formula to common adult heights, with BMI rounded to one decimal place. The 5 feet 9 inches row matches the CDC’s published example of 125 to 168 pounds for a healthy weight.
| Height | Underweight (under 18.5) | Healthy weight (18.5 to 24.9) | Overweight (25 to 29.9) | Obesity (30 or more) |
|---|---|---|---|---|
| 4 ft 10 in | 88 lb or less | 89 to 119 lb | 120 to 143 lb | 144 lb or more |
| 5 ft 0 in | 94 lb or less | 95 to 127 lb | 128 to 153 lb | 154 lb or more |
| 5 ft 2 in | 100 lb or less | 101 to 136 lb | 137 to 163 lb | 164 lb or more |
| 5 ft 4 in | 107 lb or less | 108 to 145 lb | 146 to 174 lb | 175 lb or more |
| 5 ft 6 in | 114 lb or less | 115 to 154 lb | 155 to 185 lb | 186 lb or more |
| 5 ft 8 in | 121 lb or less | 122 to 164 lb | 165 to 196 lb | 197 lb or more |
| 5 ft 9 in | 124 lb or less | 125 to 168 lb | 169 to 202 lb | 203 lb or more |
| 5 ft 10 in | 128 lb or less | 129 to 173 lb | 174 to 208 lb | 209 lb or more |
| 6 ft 0 in | 136 lb or less | 137 to 183 lb | 184 to 220 lb | 221 lb or more |
| 6 ft 2 in | 143 lb or less | 144 to 194 lb | 195 to 233 lb | 234 lb or more |
| 6 ft 4 in | 151 lb or less | 152 to 204 lb | 205 to 246 lb | 247 lb or more |
How to calculate BMI for women and men
You calculate BMI the same way for women and men, and adults use the same categories. The CDC says to interpret BMI for adults 20 and older using standard categories regardless of age or sex (CDC BMI FAQ).
How to calculate BMI for kids and teens
For children and teens ages 2 through 19, you use the same formula, but the result is compared with other children of the same sex and age. That comparison is the BMI-for-age percentile, read from CDC growth charts. The CDC’s child and teen BMI categories are:
| BMI category | BMI-for-age percentile |
|---|---|
| Underweight | Less than the 5th percentile |
| Healthy weight | 5th to less than the 85th percentile |
| Overweight | 85th to less than the 95th percentile |
| Obesity | 95th percentile or greater |
| Severe obesity | 120% of the 95th percentile or greater, or a BMI of 35 or greater |
For example, the CDC notes that a 12-year-old girl who is 5 feet tall and weighs 136 pounds has a BMI of 26.6, which is at the 96th percentile and falls in the obesity category. The same BMI in an adult would be in the overweight range, which is why adult charts should not be used for children.
How to calculate BMI in Excel
To calculate BMI for a list of people in Excel or Google Sheets, put weight in column B and height in column C, then enter one of these formulas in row 2 and copy it down:
- Pounds and inches:
=ROUND(B2/(C2^2)*703,1) - Kilograms and meters:
=ROUND(B2/(C2^2),1) - Kilograms and centimeters:
=ROUND(B2/(C2^2)*10000,1)
What BMI does not tell you
BMI is a quick, low-cost screening measure, but it is not a direct measure of body fat. According to the CDC, BMI cannot distinguish fat from muscle and bone, and it cannot show where fat is located in the body. The NHLBI adds that it does not take muscle mass, bone density or body composition into account.
The WHO notes that other measures, such as waist circumference, can also be used to identify overweight or obesity. A health care provider looks at BMI together with a physical exam, lab results and health habits. If you are tracking fitness rather than weight, see our guides to target heart rate by age and progressive overload in strength training, or compare whether rucking burns more calories than walking. For diet basics, read about the six essential nutrients.
Frequently asked questions
What is the formula to calculate BMI?
BMI equals weight in kilograms divided by height in meters squared. In U.S. units, divide weight in pounds by height in inches squared and multiply the result by 703.
How do you calculate BMI in pounds and inches?
Multiply your height in inches by itself, divide your weight in pounds by that number, then multiply by 703. For example, 200 pounds at 68 inches gives 200 divided by 4,624, times 703, which is a BMI of 30.4.
What is a healthy BMI?
For adults 20 and older, the CDC defines a healthy weight as a BMI of 18.5 to less than 25. A BMI under 18.5 is underweight, 25 to less than 30 is overweight, and 30 or higher is obesity.
Is BMI calculated differently for men and women?
No. Adults 20 and older use the same formula and the same BMI categories regardless of sex, according to the CDC. For children and teens, the BMI is compared with percentiles for the same sex and age.
Is BMI accurate for athletes?
Not always. BMI cannot tell fat from muscle and bone, so a person with a lot of muscle can have a BMI in the overweight or obesity range without having excess body fat.
Sources
- CDC: BMI Frequently Asked Questions
- CDC: Adult BMI Categories
- CDC: Child and Teen BMI Categories
- NHLBI: Calculate Your BMI
- WHO: Obesity and Overweight Fact Sheet
Image: body mass index chart by InvictaHOG, public domain, converted and resized, via Wikimedia Commons. This guide is general information, not medical advice.
