How to use this BMI calculator
- Choose your units: feet, inches and pounds, or centimeters and kilograms.
- Enter your height and weight. Use a recent weight measured without heavy clothing or shoes.
- Read your BMI and category. The scale shows where your number falls, and the results list the weight range that corresponds to a healthy BMI at your height.
- Copy the link if you want to save the result or compare it later.
How BMI is calculated
BMI is your weight divided by the square of your height. In metric units it is expressed in kilograms per square meter:
BMI = weight (kg) / height (m)²
With pounds and inches, the CDC multiplies by 703 to convert the units:
BMI = 703 × weight (lb) / height (in)²
Worked example
Someone who is 5′ 9″ (69 inches) and weighs 160 lb: 69² = 4,761, and 703 × 160 ÷ 4,761 = 23.6, which the CDC classifies as healthy weight.
In metric units, 175 cm and 70 kg: 1.75 m squared is 3.0625, and 70 ÷ 3.0625 = 22.9. The two formulas agree to within rounding, because 703 is a rounded conversion factor.
Adult BMI categories
For adults 20 and older, the CDC uses these categories. They are the same for men and women and at every adult age.
| Category | BMI |
|---|---|
| Underweight | below 18.5 |
| Healthy weight | 18.5 to 24.9 |
| Overweight | 25.0 to 29.9 |
| Obesity (class 1) | 30.0 to 34.9 |
| Obesity (class 2) | 35.0 to 39.9 |
| Obesity (class 3, severe) | 40 or higher |
To find the healthy weight range for a height, run the formula backward: weight = BMI × height² (÷ 703 in US units). At 5′ 9″, BMI 18.5 is 125 lb and BMI 24.9 is 169 lb.
BMI chart for adults: weight by height
Find your height, then compare your weight with the columns. Each weight is where that BMI begins, rounded to the nearest pound: below the BMI 18.5 weight is underweight, at or above the BMI 25 weight is overweight, and at or above the BMI 30 weight is obesity.
| Height | Metric | BMI 18.5 | Healthy range | BMI 25 | BMI 30 |
|---|---|---|---|---|---|
| 4′ 10″ | 147 cm | 89 lb | 89 lb–119 lb | 120 lb | 144 lb |
| 4′ 11″ | 150 cm | 92 lb | 92 lb–123 lb | 124 lb | 149 lb |
| 5′ 0″ | 152 cm | 95 lb | 95 lb–128 lb | 128 lb | 154 lb |
| 5′ 1″ | 155 cm | 98 lb | 98 lb–132 lb | 132 lb | 159 lb |
| 5′ 2″ | 157 cm | 101 lb | 101 lb–136 lb | 137 lb | 164 lb |
| 5′ 3″ | 160 cm | 104 lb | 104 lb–141 lb | 141 lb | 169 lb |
| 5′ 4″ | 163 cm | 108 lb | 108 lb–145 lb | 146 lb | 175 lb |
| 5′ 5″ | 165 cm | 111 lb | 111 lb–150 lb | 150 lb | 180 lb |
| 5′ 6″ | 168 cm | 115 lb | 115 lb–154 lb | 155 lb | 186 lb |
| 5′ 7″ | 170 cm | 118 lb | 118 lb–159 lb | 160 lb | 192 lb |
| 5′ 8″ | 173 cm | 122 lb | 122 lb–164 lb | 164 lb | 197 lb |
| 5′ 9″ | 175 cm | 125 lb | 125 lb–169 lb | 169 lb | 203 lb |
| 5′ 10″ | 178 cm | 129 lb | 129 lb–174 lb | 174 lb | 209 lb |
| 5′ 11″ | 180 cm | 133 lb | 133 lb–179 lb | 179 lb | 215 lb |
| 6′ 0″ | 183 cm | 136 lb | 136 lb–184 lb | 184 lb | 221 lb |
| 6′ 1″ | 185 cm | 140 lb | 140 lb–189 lb | 190 lb | 227 lb |
| 6′ 2″ | 188 cm | 144 lb | 144 lb–194 lb | 195 lb | 234 lb |
| 6′ 3″ | 191 cm | 148 lb | 148 lb–199 lb | 200 lb | 240 lb |
| 6′ 4″ | 193 cm | 152 lb | 152 lb–205 lb | 205 lb | 246 lb |
For a metric reading, one pound is 0.4536 kg; the calculator above does the conversion for you. To see what one of these weights means in daily calories, try the BMR calculator or the calorie calculator.
What BMI does not tell you
BMI is quick and free, and it is widely used for screening. The CDC is clear that it is one potential health indicator and should be considered with other factors. Its main blind spots:
- Muscle vs. fat. BMI cannot distinguish fat from muscle and bone. A very muscular person can land in the overweight or obesity range with little body fat. At 5′ 9″, 200 lb is a BMI of 29.5 no matter what the weight is made of.
- Where fat is stored. BMI does not show fat location. The NIH notes that people with overweight or obesity are more likely to have weight-related health problems when extra fat sits around the abdomen, and it lists a waist size of 35 inches or more for women, or 40 inches or more for men, as a sign of higher obesity-related risk.
- Age. Older adults tend to lose muscle and bone and gain fat, so body fat can rise while BMI stays the same.
- Ancestry. The NIH notes that some people with Asian ancestry tend to store extra fat around the waist, something BMI does not capture.
- Children and teens. The adult categories do not apply to anyone under 20. Ages 2 through 19 are assessed with BMI-for-age percentiles, which compare a child with others of the same sex and age; use the CDC Child and Teen BMI Calculator.
For a fuller picture, pair BMI with a body fat estimate from the body fat calculator, or compare formula-based targets with the ideal weight calculator. If your BMI is outside the healthy range, a doctor can tell you whether it matters for you.
BMI vs. body fat percentage
BMI does not measure body fat directly, but the CDC says it is moderately to strongly associated with more direct measures of body fat. That makes it a reasonable first check, not a final answer. Body fat percentage, estimated with methods such as skinfold calipers or tape-measure formulas, looks at body composition more directly, but it takes more effort and results vary with the method. Using both gives a fuller picture: BMI for a quick, repeatable number and a waist or body fat measurement to see what is behind it.
Frequently asked questions
What is a healthy BMI for adults?
For adults 20 and older, the CDC classifies a BMI from 18.5 to just under 25 as a healthy weight. Below 18.5 is underweight, 25 to under 30 is overweight, and 30 or higher is obesity. At 5′ 9″, that healthy band works out to about 125 lb to 169 lb. BMI is a screening number, so a doctor looks at it alongside other measures of health.
How do I calculate my BMI by hand?
Divide your weight in kilograms by your height in meters squared. In US units, multiply your weight in pounds by 703 and divide by your height in inches squared. For 160 lb at 69 inches, that is 703 × 160 ÷ 4,761 = 23.6. Round the result to one decimal place before looking up the category.
Is BMI accurate for muscular people and athletes?
Not always. BMI cannot tell muscle from fat, so a very muscular person can have a high BMI without much body fat. At 5′ 9″, a weight of 200 lb gives a BMI of 29.5 whether that weight is mostly muscle or mostly fat. A waist measurement or a body fat estimate adds useful context in that situation.
Can I use this BMI calculator for children or teens?
No. For ages 2 through 19, BMI is interpreted with BMI-for-age percentiles that compare a child with others of the same sex and age. The adult cutoffs used here do not apply. Use the CDC Child and Teen BMI Calculator and discuss the result with your child’s doctor.
Does BMI mean the same thing as I get older?
The adult categories are the same at every age, but what they tell you can change. The NIH notes that older adults tend to lose bone and muscle and gain body fat as they age, so body fat can rise even when BMI stays the same. That is one reason a doctor may also consider waist size, strength and other health markers for older adults.
What BMI is considered obese?
For adults, a BMI of 30 or higher falls in the obesity category. The CDC splits it into three classes: class 1 is 30 to under 35, class 2 is 35 to under 40, and class 3, also called severe obesity, is 40 or higher. At 5′ 9″, a BMI of 30 corresponds to about 203 lb.
Are BMI categories different for men and women?
No. For adults 20 and older, the CDC uses the same BMI categories regardless of age, sex or race. BMI itself is only a measure of weight relative to height; it does not directly measure body fat or show where fat is stored. The NIH notes, for example, that some people with Asian ancestry tend to store extra fat around the waist.