BMI Calculator
Enter your height and weight to see your body mass index, what it means and the healthy weight range for your height. Works in centimeters and kilograms, feet and pounds, or stones.
Free · No sign-up
This calculator gives an estimate for general information only and is not medical advice.
How to use it
- Choose your units: metric, US (feet, inches and pounds) or UK (feet, inches, stones and pounds).
- Enter your height and weight. Your BMI, its category and the colored scale update as you type.
- Read your healthy weight range and how far you are from it.
- Optional: open More options to pick a different standard, add your age for age-specific notes, or add your waist to get your waist-to-height ratio.
Why use this tool
Metric, US and UK units
Centimeters and kilograms, feet and pounds, or stones and pounds. Values convert automatically when you switch.
Healthy weight range
See the weight range that counts as healthy for your height, and how far above or below it you are.
Four official standards
WHO categories, lower thresholds for people of Asian and other backgrounds, and the official Japanese and Chinese classifications.
Waist-to-height ratio
Add your waist to see a second measure that reflects belly fat, using the thresholds in NICE guidance.
Notes for age
Under 18, the calculator explains why adult categories do not apply. Notes also cover ages 18 to 19 and 65 and over.
Private
Everything is calculated in your browser. Your height, weight and waist are not saved or sent anywhere.
BMI categories for adults
Body mass index is your weight in kilograms divided by the square of your height in meters. The same categories apply to adult women and men. Some health bodies use lower thresholds for people with a higher risk of type 2 diabetes and heart disease at a lower weight.
| Category | WHO (international) | Asian and other backgrounds (WHO, NICE) | Japan (JASSO) | China (WS/T 428) |
|---|---|---|---|---|
| Underweight | below 18.5 | below 18.5 | below 18.5 | below 18.5 |
| Healthy weight | 18.5 to 24.9 | 18.5 to 22.9 | 18.5 to 24.9 | 18.5 to 23.9 |
| Overweight | 25 to 29.9 | 23 to 27.4 | – | 24 to 27.9 |
| Obesity | 30 or more | 27.5 or more | 25 or more (grades 1 to 4) | 28 or more |
How to calculate BMI
Metric formula: BMI = weight (kg) ÷ height (m)². For example, 70 kg and 1.75 m give 70 ÷ (1.75 × 1.75) = 22.9.
US formula: BMI = 703 × weight (lb) ÷ height (in)². For example, 154 lb and 5 ft 9 in (69 inches) give 703 × 154 ÷ (69 × 69) = 22.7.
To find a healthy weight range for your height, reverse the formula: multiply your height in meters squared by 18.5 and by 24.9.
Healthy weight for height chart
The healthy range below uses the WHO limits of 18.5 to 24.9. For people of Asian, Middle Eastern, Black African or African-Caribbean background, the upper limit is lower (22.9).
| Height (cm) | Height (ft, in) | Healthy weight (kg) | Healthy weight (lb) |
|---|---|---|---|
| 150 | 4 ft 11 in | 41.6–56.0 | 92–124 |
| 155 | 5 ft 1 in | 44.4–59.8 | 98–132 |
| 160 | 5 ft 3 in | 47.4–63.7 | 104–141 |
| 165 | 5 ft 5 in | 50.4–67.8 | 111–149 |
| 170 | 5 ft 7 in | 53.5–72.0 | 118–159 |
| 175 | 5 ft 9 in | 56.7–76.3 | 125–168 |
| 180 | 5 ft 11 in | 59.9–80.7 | 132–178 |
| 185 | 6 ft 1 in | 63.3–85.2 | 140–188 |
| 190 | 6 ft 3 in | 66.8–89.9 | 147–198 |
What BMI does not tell you
BMI is a quick screening measure, not a diagnosis. It does not separate fat from muscle and does not show where fat is stored.
- Muscular people, such as athletes, can have a high BMI without excess fat.
- From age 65, muscle loss and height loss make BMI less precise.
- During pregnancy, BMI does not apply. Ask your midwife or doctor.
- Children and teenagers need BMI-for-age percentiles, not the adult categories.
- Belly fat carries more health risk than fat elsewhere, which is why the waist-to-height ratio is a useful second measure.
Waist-to-height ratio
Divide your waist by your height, using the same unit for both. NICE guidance for adults uses these thresholds: under 0.5 is healthy, 0.5 to 0.59 means increased health risk, and 0.6 or more means high health risk. In practice: keep your waist to less than half your height.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI from 18.5 to 24.9 is in the healthy range. For people of Asian, Middle Eastern, Black African or African-Caribbean background, health bodies such as NICE use 18.5 to 22.9, because health risks rise at a lower BMI.
Is BMI different for women and men?
No. Adults of both sexes use the same formula and the same categories. Women usually have more body fat than men at the same BMI, which is one reason BMI is only a screening measure.
Can I use this BMI calculator for children?
It calculates the number, but the adult categories do not apply under 18. For children and teenagers, BMI is compared with growth charts for the same age and sex, and the result is a percentile. A doctor or school nurse can check this for you.
Why are the thresholds lower for people of Asian background?
Research summarized by a WHO expert consultation in 2004 found that many Asian populations have a higher risk of type 2 diabetes and heart disease at a lower BMI. NICE guidance applies the same lower thresholds to people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background.
Is BMI accurate for athletes?
Not always. BMI cannot tell muscle from fat, so very muscular people can be classed as overweight while having little body fat. The waist-to-height ratio or a body composition measurement gives a better picture.
How do I calculate BMI in pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. For 154 lb and 69 inches: 703 × 154 ÷ 4,761 = 22.7.
Are my height and weight saved?
No. The calculation happens in your browser and nothing is sent to a server. The page only remembers your preferred units and standard.
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