How do you calculate BMI?

Divide weight in kilograms by height in metres squared. At 1.75 m and 80 kg: 1.75 × 1.75 = 3.0625, and 80 ÷ 3.0625 = 26.1. In US units, multiply pounds by 703 and divide by inches squared: 150 lb at 5 ft 6 in (66 in) is 703 × 150 ÷ 4,356 = 24.2.

What is a healthy BMI?

18.5 to 24.9 for adults, by the CDC and WHO. Below 18.5 is underweight, 25 to 29.9 overweight and 30 or more obesity. On the Asia-Pacific scale the healthy band ends at 22.9. The page turns that band into a weight range for your height.

What should I weigh for my height?

Any weight that puts BMI between 18.5 and 24.9: 18.5 × height² to 24.9 × height², in metres and kilograms. At 1.65 m that is 50.4 to 67.8 kg; at 5 ft 10 in it is about 129 to 174 lb. The 'Healthy weight for your height' line on the result does this for you.

Why do I get a different BMI category on different websites?

Most calculators show only the global cut-offs. This one also shows the Asia-Pacific scale, which calls a BMI of 23 to 24.9 overweight rather than healthy and 25 or more obese. Older pages may also still use 'normal weight' for what the CDC now calls 'healthy weight'; the band is the same.

Is BMI accurate for athletes, older people or different ethnic groups?

Less so. It overstates fatness in very muscular people, can understate it in older adults who have lost muscle, and the risk at a given BMI differs between populations, which is why Asian populations have their own lines. The CDC describes BMI as one potential health indicator to be considered with other factors.

Is a BMI of 25 overweight?

Yes, on the global scale: overweight starts at exactly 25.0. 24.9 is the top of the healthy range. On the Asia-Pacific scale, 25 is already the start of obesity. A single point either side of a line means very little for one person; the trend over time tells more.

BMI Calculator: Body Mass Index and Healthy Weight Range

Body Mass Index from height and weight, with the CDC/WHO adult categories, the Asia-Pacific cut-offs and the healthy weight range for your height.

Inputs

Height(cm)

50 cm250 cm

Weight(kg)

2 kg300 kg

Units

Include CalculateEveryday mark

BMI

22.5

Healthy weight

UnderHealthyOverObesity

WHO global category: Healthy weight
WHO Asia-Pacific category: Healthy weight
Working (kg, m): 65.0 ÷ 1.70² = 65.0 ÷ 2.89 = 22.5
Healthy weight for your height (BMI 18.5–24.9): 53.5 kg – 72.0 kg
Asia-Pacific healthy range (BMI 18.5–22.9): 53.5 kg – 66.2 kg
Distance from the range: Inside the healthy range

BMI doesn't distinguish muscle from fat and doesn't account for age, sex, or build.
For anyone under 20, the CDC uses BMI-for-age percentiles instead of these adult categories.

Use this calculator on your own site

Free embed

Two lines of HTML, unlimited views
Shows a small CalculateEveryday bar, with a credit link under the calculator

What each BMI input means

Height: Standing height without shoes, in centimetres or, in US units, in inches — 5 ft 9 in is 69 in. A centimetre of error moves BMI by about 0.3 at average heights.
Weight: Weight in light clothing, ideally first thing in the morning. Day-to-day swings of a kilogram or two are normal and move BMI by well under one point.
Units: Metric takes centimetres and kilograms; US takes inches and pounds and uses the CDC's 703 × lb ÷ in² form. Both give the same BMI.

BMI formula

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

\text{BMI} = \frac{\text{weight (kg)}}{\text{height (m)}^2} = 703 \times \frac{\text{weight (lb)}}{\text{height (in)}^2}

Body Mass Index divides weight by the square of height, so that people of different heights can be compared on one scale. In metric units it is kilograms divided by metres squared; in US units the CDC multiplies pounds by 703 and divides by inches squared, the 703 folding the unit conversion into one number. The adult categories used by the CDC and the WHO are the same: under 18.5 is underweight, 18.5 to under 25 is a healthy weight, 25 to under 30 is overweight, and 30 or more is obesity, split into class 1 (30 to under 35), class 2 (35 to under 40) and class 3 (40 and over). Because people of Asian descent show diabetes and heart-disease risk at lower BMIs, the WHO's Western Pacific office set lower lines for the region in 2000 — overweight from 23 and obese from 25 — and the page shows that category beside the global one. Run backwards, the same formula gives the healthy weight range for your height: 18.5 × height² to 24.9 × height². The CDC is explicit that BMI is a screening measure, one indicator to be read with others, not a diagnosis of body fat or health.

BMI worked example

An adult 170 cm tall weighing 65 kg: 1.70 squared is 2.89, and 65 ÷ 2.89 = 22.5. That sits in the healthy range on both scales — under 25 globally and under 23 on the Asia-Pacific scale. The healthy weight range for 170 cm is 18.5 × 2.89 = 53.5 kg up to 24.9 × 2.89 = 72.0 kg, or up to 66.2 kg on the Asia-Pacific lines.

More BMI examples

A man 5 ft 9 in (69 in) tall weighing 200 lb: 703 × 200 = 140,600, divided by 69² = 4,761, gives a BMI of 29.5 — overweight on the global scale, one point short of obesity class 1, and obese on the Asia-Pacific scale. The healthy range at his height is 125.3 to 168.6 lb, the same 125–168 lb the CDC's own height-weight table shows for 5 ft 9 in, so he is 31.4 lb above its top.

A woman 160 cm tall weighing 45 kg: 1.6² = 2.56, and 45 ÷ 2.56 = 17.6, which is underweight on both scales. The bottom of the healthy range at 160 cm is 18.5 × 2.56 = 47.4 kg, 2.4 kg more than she weighs now.

Where the BMI calculator can give the wrong answer

BMI cannot tell muscle from fat. A muscular athlete can read 'overweight' with little body fat, and an older adult who has lost muscle can read 'healthy' while carrying a high share of fat. Waist circumference or a body-fat estimate fills that gap.
The adult categories apply from age 20. For children and teens the CDC compares BMI with growth-chart percentiles for the same age and sex, so a BMI of 22 can be healthy at 17 and high at 10; this calculator does not do that comparison.
The WHO global cut-offs were drawn mostly from European and North American data. The Asia-Pacific lines exist because South and East Asian populations show cardiovascular and diabetes risk at lower BMIs, so the page reports both rather than leaving a reader of Asian descent with the global scale alone.
Pregnancy changes weight for reasons BMI was not built for; pre-pregnancy BMI is what weight-gain guidance uses.
Rounding: the headline shows one decimal, so 24.96 reads 25.0 and falls in 'overweight' while 24.94 reads 24.9 and does not. Near a line, either side is the same body.

Spotted a mistake? Tell us

BMI reference table

Adult BMI categories
Category	Global (CDC and WHO)	Asia-Pacific (WHO WPRO 2000)
Underweight	Below 18.5	Below 18.5
Healthy weight	18.5 to 24.9	18.5 to 22.9
Overweight	25.0 to 29.9	23.0 to 24.9
Obesity class 1	30.0 to 34.9	25 and over (obese)
Obesity class 2	35.0 to 39.9	—
Obesity class 3	40 and over	—

Source: CDC, 'Adult BMI Categories'; WHO Western Pacific Region, 'The Asia-Pacific perspective: redefining obesity and its treatment' (2000)

BMI FAQ

: Divide weight in kilograms by height in metres squared. At 1.75 m and 80 kg: 1.75 × 1.75 = 3.0625, and 80 ÷ 3.0625 = 26.1. In US units, multiply pounds by 703 and divide by inches squared: 150 lb at 5 ft 6 in (66 in) is 703 × 150 ÷ 4,356 = 24.2.
: 18.5 to 24.9 for adults, by the CDC and WHO. Below 18.5 is underweight, 25 to 29.9 overweight and 30 or more obesity. On the Asia-Pacific scale the healthy band ends at 22.9. The page turns that band into a weight range for your height.
: Any weight that puts BMI between 18.5 and 24.9: 18.5 × height² to 24.9 × height², in metres and kilograms. At 1.65 m that is 50.4 to 67.8 kg; at 5 ft 10 in it is about 129 to 174 lb. The 'Healthy weight for your height' line on the result does this for you.
: Most calculators show only the global cut-offs. This one also shows the Asia-Pacific scale, which calls a BMI of 23 to 24.9 overweight rather than healthy and 25 or more obese. Older pages may also still use 'normal weight' for what the CDC now calls 'healthy weight'; the band is the same.
: Less so. It overstates fatness in very muscular people, can understate it in older adults who have lost muscle, and the risk at a given BMI differs between populations, which is why Asian populations have their own lines. The CDC describes BMI as one potential health indicator to be considered with other factors.
: Yes, on the global scale: overweight starts at exactly 25.0. 24.9 is the top of the healthy range. On the Asia-Pacific scale, 25 is already the start of obesity. A single point either side of a line means very little for one person; the trend over time tells more.