What is a healthy BMI?
For adults, a BMI of 18.5 to 24.9 is the normal, healthy range. With the lower cut-offs, healthy ends at 22.9 instead.
BMI Calculator
Calculate your BMI from your height and weight, see where it sits on the BMI chart and the healthy weight range for your height.
Height
cm
cmft, in
Weight
kg
kglbst
Age
years
Leave empty for adults.
Months
For ages 2 to 19.
Sex
MaleFemale
Used for ages 2 to 19. Adult BMI ranges are the same for men and women.
22.5Healthy weight
170 cm and 65 kg give a BMI of 22.5: healthy weight for an adult.
Your BMI category
Healthy weight for your height
- Healthy BMI
- 18.5 to 24.9
- Healthy weight
- 53.5 to 72.0 kg
- Your weight
- In the healthy range
Working
BMI = 65 ÷ (1.7 × 1.7) = 65 ÷ 2.89 = 22.5
Details
- BMI Prime
- 0.90
- Ponderal index
- 13.2 kg/m³
- Waist-to-height ratio
- Add your waist in the settings
A screening measure, not a diagnosis: BMI cannot tell muscle from fat and is not used in pregnancy. A doctor or nurse can say what your number means for you.
Cut-offs
StandardLower
WHO ranges. Lower suits Asian, Black and Middle Eastern family backgrounds (NICE).
Waist
cm
Optional. Measure halfway between your lowest rib and the top of your hip, breathing out.
BMI chart for 170 cm
| Category | BMI | Weight |
|---|---|---|
| Underweight | Under 18.5 | Under 53.5 kg |
| Healthy weight | 18.5 to 24.9 | 53.5 to 72.0 kg |
| Overweight | 25 to 29.9 | 72.2 to 86.4 kg |
| Obesity class 1 | 30 to 34.9 | 86.7 to 100.9 kg |
| Obesity class 2 | 35 to 39.9 | 101.1 to 115.3 kg |
| Obesity class 3 | 40 or more | 115.6 kg or more |
What is my BMI? Type your height and weight in metric or imperial units, and the answer and its category update as you type.
No account and no email: the measurements you enter stay in this browser tab and are never uploaded or kept.
- Adults, children and teens
- Kilograms, pounds or stones
- Healthy weight for your height
How to calculate BMI
Two measurements give an adult's BMI; a child's also needs age and sex for the growth chart.
Enter your height
Type your height in centimetres, or press ft, in beside the box to use feet and inches. Mixed units work too.
Add weight and age
Give your weight in kg, lb or stones and pounds. Age and sex only change the answer for children aged 2 to 19.
Read your BMI
Your BMI appears at once with its category on the BMI scale, your healthy weight range and how far you are off it.
BMI formula in kg and pounds
The BMI formula is weight in kilograms divided by height in metres squared: BMI = kg ÷ m². For 65 kg at 170 cm, the height is 1.70 m, 1.70 × 1.70 = 2.89 and 65 ÷ 2.89 = 22.5. The answer is rounded to one decimal before its category is read.
In pounds and inches the equation becomes BMI = 703 × lb ÷ in². At 5 ft 7 in, which is 67 inches, and 150 lb: 67 × 67 = 4,489, then 703 × 150 ÷ 4,489 = 23.5. The 703 only converts the units, so both formulas give one BMI for one body.
This calculator converts feet, inches, stones and pounds exactly (an inch is 2.54 cm, a pound 0.45359237 kg) and the Working block shows each step with your own numbers. BMI Prime divides your BMI by 25, the top of the healthy range, so 1.0 is its edge.
BMI chart for adults
From age 20 the World Health Organization chart uses the same BMI ranges for women and men: under 18.5 is underweight, 18.5 to 24.9 healthy weight, 25 to 29.9 overweight and 30 or more obesity, split into class 1 (30 to 34.9), class 2 (35 to 39.9) and class 3 (40 and over).
Health risks rise at a lower BMI for many people of South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean family background. NICE in the UK puts overweight at 23 to 27.4 and obesity at 27.5 or more for them: pick Lower in the settings to use these cut-offs.
The chart under the calculator turns every category into a weight range for your height. At 170 cm a healthy weight runs from 53.5 to 72.0 kg, and at 5 ft 7 in from 118.1 to 159.0 lb. BMI is a quick screening number: it cannot weigh muscle against fat, so a waist measure adds a second check.
BMI for children and teens
Children and teens are still growing, so their BMI is compared with others of the same age and sex on the CDC growth charts. The answer is a percentile: a BMI at the 70th percentile is higher than that of 70 in every 100 children of that age and sex.
From age 2 to 19, under the 5th percentile is underweight, the 5th to under the 85th is a healthy weight, the 85th to under the 95th is overweight and the 95th or above is obesity. Severe obesity starts at 120% of the 95th percentile, or a BMI of 35.
Type the age in years and months and pick the sex, and the calculator places the BMI on the CDC 2000 BMI-for-age chart. For a 10-year-old boy, a BMI of 18.6 is at the 78th percentile, a healthy weight, and the healthy range at that age is a BMI of 14.2 to 19.4.
A BMI calculator for women and men
Metric or imperial
Height in cm or feet and inches, weight in kg, pounds or stones, in any mix, such as kg and feet.
BMI for teens and kids
For ages 2 to 19, the BMI-for-age percentile from the CDC growth charts for that age and sex.
Healthy weight range
The weights that give a healthy BMI at your height, and how many kg or lb you are above or below.
Asian BMI cut-offs
Switch to NICE's lower cut-offs of 23 and 27.5, used for Asian, Black and Middle Eastern origins.
Waist-to-height ratio
Add your waist to see the ratio NICE reads beside BMI. Keep your waist under half your height.
Your own BMI chart
A table of every BMI category as a weight range for your height, with your own band marked.
Your height and weight stay private
Every number is worked out on your device. Your measurements are never sent, saved or linked to you.
Processing
Your browser works out the BMI, the percentile and the weight range. No measurement goes online.
Storage
Nothing is remembered. A reload puts the boxes back to the example, and no history is kept at all.
Account
Use this free BMI calculator for yourself or your family as often as you like, with no sign-up.
Questions about BMI
What BMI is considered obese?
A BMI of 30 or more for adults, or 27.5 or more with the lower cut-offs. Class 2 obesity starts at 35 and class 3 at 40.
What is a good BMI for women?
The same as for men: 18.5 to 24.9. Women carry more body fat than men at an equal BMI, but the adult ranges stay the same.
What does BMI stand for?
Body mass index: weight in kg divided by height in metres squared. Quetelet made it in 1832; Ancel Keys named it in 1972.
Is BMI accurate for everyone?
No. It cannot tell muscle from fat, so athletes can read as overweight, and it is not used in pregnancy. Waist size helps.
How much should I weigh for my height?
Enough for a BMI of 18.5 to 24.9. At 170 cm that is 53.5 to 72.0 kg; at 5 ft 7 in it is 118 to 159 lb. Type yours above.
What BMI is overweight?
25 to 29.9 for adults, or 23 to 27.4 with the lower cut-offs. For under-20s it is the 85th to under the 95th percentile.
Does BMI change with age?
Not for adults: the ranges stay fixed from age 20. Under 20, one BMI means something different at each age and for each sex.
Still stuck, or found a problem? Email dobliquestudio@gmail.com and we will help.