BMI calculator

Body mass index compares your weight to your height. The formula is:

• Metric: BMI = weight (kg) ÷ height (m)²
• US units: BMI = 703 × weight (lb) ÷ height (in)²

Example: you're 5 ft 9 in (69 inches) and weigh 160 lb. 69 × 69 = 4,761. 160 ÷ 4,761 = 0.0336, and 0.0336 × 703 = 23.6. That falls in the normal weight range.

The calculator rounds BMI to one decimal place, which is how it's usually reported. You can switch between US and metric units at any time; the result is the same either way.

The calculator uses the World Health Organization's adult categories, which the CDC and NIH use as well (the WHO splits underweight and obesity into finer grades):

BMI	Category
Below 18.5	Underweight (severe, moderate or mild thinness)
18.5 – 24.9	Normal (healthy) weight
25.0 – 29.9	Overweight
30.0 – 34.9	Obesity class I
35.0 – 39.9	Obesity class II
40 and above	Obesity class III

The colored bar shows where you fall on this scale, and the table highlights your row.

Here's the weight range for a normal BMI (18.5–24.9) at common adult heights, rounded inward to whole pounds:

Height	Normal weight range
5 ft 0 in	95 – 127 lb
5 ft 3 in	105 – 140 lb
5 ft 6 in	115 – 154 lb
5 ft 9 in	126 – 168 lb
6 ft 0 in	137 – 183 lb
6 ft 3 in	149 – 199 lb

A weight above the top of the range gives a BMI of 25 or more (overweight); below the bottom, a BMI under 18.5 (underweight). For any other height, just enter it in the calculator above.

Below the categories you'll see the weight range that gives a BMI between 18.5 and 24.9 at your height. For example, at 5 ft 9 in that's roughly 126 to 168 lb; at 5 ft 4 in it's roughly 108 to 145 lb.

This range is a screening guide, not a target you must hit. If you want a single number, the ideal weight calculator compares the classic Devine, Robinson, Miller and Hamwi formulas.

BMI is quick and useful for large groups, but it has well-known limits for individuals:

• Muscle vs. fat. BMI can't tell them apart. Muscular athletes often land in the "overweight" range while being lean.
• Older adults lose muscle with age, so a "normal" BMI can hide extra body fat.
• Pregnancy changes weight for reasons BMI doesn't account for. Use the pregnancy weight gain calculator instead.
• Fat distribution matters. Belly fat carries more health risk than fat on the hips, and BMI ignores it. Your waist-to-hip ratio or waist measurement adds that information.
• Ethnicity: some groups, including many people of Asian descent, have higher health risks at lower BMI values.

For a fuller picture, pair BMI with a body fat estimate and talk to your doctor.

Adult categories don't apply under age 20. For children and teens, BMI is compared with growth charts for the same age and sex and reported as a percentile. If you enter an age under 20, the calculator reminds you of this instead of showing an adult category. Your child's pediatrician can plot the percentile for you.

This calculator is for information only and isn't medical advice. Everything happens in your browser; your numbers are never uploaded.

For ages 2 to 20, the BMI calculator for kids works out the BMI percentile from CDC growth charts and plots your child on the curve.