BMI Calculator
Enter your height and weight to instantly see your BMI, its category, and your ideal weight (BMI 22).
1. Enter your height and weight
As you type, your BMI and category appear right away.
Units
2. Results
Choose the classification. The copy buttons copy just the number.
- BMI
- —
- Category
- —
- Ideal weight (BMI 22)
- —
- Difference from ideal weight
- —
- Normal weight range
- —
Classification
Everything is calculated on this device. The numbers you enter are never sent anywhere.
Categories follow the WHO (World Health Organization) classes. In Japan, JASSO counts a BMI of 25 or more as obesity.
BMI is a rough guide to body size based only on height and weight — it isn’t a diagnosis. It may not fit people with a lot of muscle, pregnant people, or children.
Found it useful? We'd love a share
Something not working, or an idea to make it better?
How to use
1. Enter your height and weight
Enter your height in cm under “Height” and your weight in kg under “Weight”. As you type, “Results” below shows your BMI, category, ideal weight (BMI 22), difference from ideal weight, and normal weight range.
On the left, enter your height in cm under “Height” and your weight in kg under “Weight”. As you type, “Results” on the right shows your BMI, category, ideal weight (BMI 22), difference from ideal weight, and normal weight range.
2. Choose the classification
Under “Results”, in “Classification”, tap “Japan (JASSO)” to switch the category to the Japan Society for the Study of Obesity classes (obesity class 1–4 from BMI 25). Tap “WHO” to go back.
Under “Results” on the right, in “Classification”, click “Japan (JASSO)” to switch the category to the Japan Society for the Study of Obesity classes (obesity class 1–4 from BMI 25). Click “WHO” to go back.
3. Enter in feet, inches and pounds
Under “Units”, tap “ft · in · lb” to enter your height in feet and inches and your weight in pounds. The ideal weight and normal weight range are shown in lb too.
On the left, under “Units”, click “ft · in · lb” to enter your height in feet and inches and your weight in pounds. The ideal weight and normal weight range are shown in lb too.
4. Copy the results
Tap the copy button to the right of a result to copy just the number (like “22.5”). “Copy all results” copies your BMI, category, ideal weight and the rest together.
Click the copy button to the right of a result to copy just the number (like “22.5”). “Copy all results” copies your BMI, category, ideal weight and the rest together.
Great for
Knowing your BMI before a check-up
Enter your height and weight to get the same BMI that appears on check-up results and health forms, with its WHO category.
Anyone with a check-up or health form coming up
Getting a reference weight to track against
See your ideal weight (BMI 22) and the weight range for a normal BMI, in kg or lb. A handy reference when you log your weight.
People who keep track of their weight
Explaining BMI in class or in a handout
Show the formula and how the WHO and Japanese classes differ, changing the numbers on the spot.
Teachers and health educators
Switching between metric and imperial
Enter figures like “5 ft 10 in, 180 lb” as they are, or switch to cm and kg — you get the same BMI either way.
Anyone reading health info from other countries
Good to know before you start
- BMI is a rough guide to body size. It doesn’t measure body fat or tell you about your health, and it reads high for people with a lot of muscle.
- Children and teens under 18 are assessed differently, using age- and sex-specific growth charts. The categories here are for adults.
- It doesn’t show “goal” or “beauty” weights such as BMI 20 or 18, because they aren’t official standards.
How BMI and ideal weight are calculated
BMI (body mass index) is your weight in kg divided by the square of your height in metres. For 170 cm and 60 kg, that’s 60 ÷ 1.7² = 20.76…, which rounds to 20.8. The ideal weight is the weight that gives a BMI of 22: your height in metres squared × 22. The Japan Society for the Study of Obesity regards a BMI of around 22 as the level linked to the lowest rates of illness.
WHO and the Japan Society for the Study of Obesity (JASSO) use the same cut-offs — 18.5, 25, 30, 35 and 40 — but name the classes differently. Because people in Asia tend to develop lifestyle-related diseases at a lower BMI, Japan counts a BMI of 25 or more as obesity. Under WHO, 25 to under 30 is “overweight” (pre-obesity), and obesity starts at 30. This tool classifies using the BMI shown on screen (to one decimal place), so the number and the category always agree.
FAQ
Answers to the things people most often wonder about when calculating BMI.
Are my height and weight sent anywhere?
No. All calculations happen in the browser on your device, and the numbers you enter are never sent to a server or stored.
How is BMI calculated?
Weight (kg) ÷ height (m) ÷ height (m), rounded to one decimal place. For example, 160 cm and 65 kg gives 65 ÷ 1.6² = 25.39…, so the BMI is 25.4.
Why is the ideal weight based on a BMI of 22?
Studies in Japan found that people with a BMI of around 22 were the least likely to have high blood pressure, diabetes or abnormal blood lipids. The Japan Society for the Study of Obesity defines standard weight as height (m) squared × 22.
What’s the difference between the WHO and Japanese (JASSO) categories?
The BMI cut-offs are the same, but 25 to under 30 has a different name: WHO calls it “Overweight”, while JASSO calls it “Obesity class 1”. This page starts with the WHO classes; switch with “Japan (JASSO)” under “Classification”.
How is the “Normal weight range” worked out?
It shows the weights that give a BMI of at least 18.5 and under 25, in steps of 0.1 kg (0.1 lb with “ft · in · lb”). Rounding is taken into account, so entering the weight at either end of the range gives “Normal weight”.
What happens to BMI if I have a lot of muscle?
It reads high. BMI uses only height and weight, so it can’t tell muscle from fat. For people who exercise a lot, a high category doesn’t necessarily mean a lot of body fat.
Can I check a child’s BMI?
You can calculate the number, but the categories are for adults. Children’s BMI changes as they grow, so it’s assessed with growth charts that compare it with other children of the same age and sex.
Can it show a goal weight for a BMI of 20 or 18?
No. Targets like BMI 20 or 18 aren’t official standards, and a BMI of 18 falls in the “Underweight” category. This tool shows the ideal weight (BMI 22) and the normal weight range.
Can I use feet and pounds?
Yes. Choose “ft · in · lb” under “Units” to enter your height in feet and inches and your weight in pounds. It converts with 1 in = 2.54 cm and 1 lb = 0.45359237 kg — for example, 5 ft 10 in and 180 lb gives a BMI of 25.8.
Can I type the unit too, like “60kg”?
Just enter the number — the unit is shown to the right of each box. If you enter your height in metres, like “1.7”, you’ll be asked to enter it in cm.
Is it free?
Yes. No sign-up or install, and no ads. Use it as often as you like.
More tools
- Tax Calculator (Add or Remove Tax)
Enter a price to instantly see the amount before tax, the tax, and the total. Japan’s 10% and 8% rates are built in, or use any rate.
- Age Calculator
Pick a date of birth to see the exact age, days until the next birthday, days lived and the Chinese zodiac sign, with an age chart by birth year.
- Date Calculator (Add or Subtract Days)
Instantly get the date and weekday N days or N business days after or before any date. Weekends and holidays can be skipped too.
- Time Calculator (Work Hours Total)
Work out hours worked from start, end and break times, and add them up. Also adds and subtracts time and converts to decimal hours.
- Bill Splitter
Enter the total and the number of people to see what each person owes. Round to an easy amount, have some people pay more, and let the organizer cover the difference.
- Days Until (Day Counter)
Instantly count how many days are left until a date, or how many days are between two dates. Include the start day, or count weekdays only.