BMI Calculator
BMI, healthy weight, BMR and daily calories in one place. Runs in your browser.
About this bmi calculator
This BMI calculator gives you your body mass index, its WHO category and the healthy weight range for your height. It also estimates your BMR, your total daily energy use (TDEE) and calorie targets for losing, keeping or gaining weight.
Enter height and weight in centimetres and kilograms, or in feet, inches and pounds. Switching units converts what you typed, so you don't have to start over. You can also switch to the lower BMI cut-offs a WHO expert group suggested for Asian populations.
It is a screening tool, not a diagnosis. BMI can't tell muscle from fat and it isn't used for children. The page says so next to your result, not hidden at the bottom.
Features
BMI with a visual scale
Your BMI to one decimal, its category, and a marker on a colour scale from 14 to 42 so you can see how far you are from each band.
WHO or Asian cut-offs
Standard WHO bands (18.5, 25, 30, 35, 40) or the Asian action points of 23 and 27.5. The scale and healthy range update with your choice.
Healthy weight range for your height
The weight that puts you between BMI 18.5 and 24.9 (or 22.9), plus how far you are above or below it.
Three BMR formulas
Mifflin-St Jeor by default, the revised Harris-Benedict equation, or Katch-McArdle if you know your body fat percentage.
TDEE and calorie targets
Five activity levels from sedentary (×1.2) to extra active (×1.9), and daily calories to lose or gain 0.25 or 0.5 kg (0.5 or 1 lb) a week.
Safety flags
A target below 1,200 kcal for women or 1,500 kcal for men is marked in red, and under-18s are told that adult categories don't apply.
How to use the bmi calculator
- 1Pick metric or imperial, then enter your sex, age, height and weight.
- 2Choose your activity level and, if you like, a BMR formula or Asian cut-offs.
- 3Read your BMI category, healthy weight range, BMR, TDEE and calorie targets.
When to use it
A quick weight check
See where you sit on the scale before a check-up, and what weight range doctors usually aim for at your height.
Planning a diet
Find your maintenance calories, then pick a loss rate that keeps you above the usual minimum intake.
Bulking for the gym
Use the gain rows for a slow surplus. If you lift, trust your waist measurement more than your BMI.
Comparing over time
Log your BMI each month. The percentage change between two readings shows your real progress better than the raw numbers.
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared. Someone who is 1.75 m tall and weighs 72 kg has a BMI of 72 ÷ (1.75 × 1.75) = 23.5.
In pounds and inches the formula is 703 × lb ÷ in². This calculator converts imperial input to metric first, so both give the same answer. If you have a height in a unit we don't take, the unit converter will turn it into centimetres.
The category is decided on the rounded value you see. A BMI of 24.96 shows as 25.0 and counts as overweight, which matches how a clinic would read it.
What are the BMI categories for adults?
The World Health Organization uses these bands for adults of any sex. The Asian cut-offs come from a 2004 WHO expert consultation, which found that many Asian people carry more health risk at a lower BMI.
- Below 18.5: underweight (WHO splits it into mild, moderate and severe thinness at 17 and 16)
- 18.5 to 24.9: healthy weight
- 25 to 29.9: overweight
- 30 to 34.9: obesity class I
- 35 to 39.9: obesity class II
- 40 and above: obesity class III
- Asian cut-offs: healthy 18.5 to 22.9, increased risk from 23, high risk from 27.5
What is the difference between BMR and TDEE?
BMR (basal metabolic rate) is the energy your body burns at complete rest: breathing, circulation, keeping warm. For most adults it is 1,200 to 2,000 kcal a day.
TDEE (total daily energy expenditure) is BMR times an activity factor. A desk worker who walks a little uses about BMR × 1.375. That number is your maintenance intake.
The Mifflin-St Jeor equation, published in 1990, is the one most dietitians use today. For a man it is 10 × kg + 6.25 × cm − 5 × age + 5. For a woman the last term is −161. Studies put it within about 10% of measured BMR for most healthy adults.
Why doesn't BMI work for everyone?
BMI only knows height and weight. A rugby player with 10% body fat can score 29 and be called overweight. An older adult who has lost muscle can score 23 and still carry too much fat around the organs.
For children and teens, BMI is compared with growth charts for their exact age and sex, so the adult bands are wrong for them. It is also not used in pregnancy. If you want a second check, measure your waist: a waist under half your height is a common rule of thumb.
Why use Mavros
| Mavros | Typical upload sites | |
|---|---|---|
| Cut-offs | WHO or Asian, your choice | WHO only |
| In one page | BMI, healthy range, BMR, TDEE and calorie targets | Separate calculators for each |
| BMR formulas | Mifflin-St Jeor, Harris-Benedict, Katch-McArdle | One formula, often unnamed |
| Unit switch | Converts what you typed | Clears the form |
| Limits | Stated beside the result, with a low-calorie warning | A disclaimer at the bottom |
| Privacy | Your weight never leaves the browser | Inputs may be logged on a server |
Tips
- Weigh yourself in the morning before eating, for a fair comparison week to week.
- If you train with weights, pick Katch-McArdle and enter a body fat reading. It accounts for muscle.
- Pick the activity level for a typical week, not your best week. Most people overestimate it.
- Losing 0.5 kg a week means about 550 kcal less than your TDEE each day. Faster than that is hard to keep up.
- Recalculate after every 4 to 5 kg change, because your BMR drops as you lose weight.
- Want to check the maths yourself? Type 72 / 1.75^2 into the scientific calculator and you get the same 23.5.
Questions
What is a healthy BMI?
For adults, a BMI from 18.5 to 24.9 is the WHO healthy range. If you are of Asian background, many health services use 18.5 to 22.9 instead, which you can turn on with the Asian cut-offs option.
How do I calculate my BMI by hand?
Divide your weight in kilograms by your height in metres, squared. At 1.65 m and 60 kg, that is 60 ÷ 2.7225 = 22.0. In imperial units, multiply pounds by 703 and divide by inches squared.
Is BMI accurate for athletes and muscular people?
No, it often overstates their risk. Muscle is denser than fat, so a lean, muscular person can land in the overweight band. Body fat percentage or waist size gives a better picture for them.
Can I use this BMI calculator for my child?
No. Children and teens are assessed with BMI-for-age percentile charts, which compare them with others of the same age and sex. The calculator shows a note instead of a category when the age is under 18.
Which BMR formula is the most accurate?
Mifflin-St Jeor is the most accurate for most people without a body fat reading. If you know your body fat, Katch-McArdle can be closer, especially for lean or muscular people. The revised Harris-Benedict tends to run slightly higher.
How many calories should I eat to lose weight?
Start about 500 kcal below your TDEE for roughly 0.5 kg (1 lb) a week. The table shows exact figures for your inputs. Women should stay above about 1,200 kcal and men above 1,500 kcal unless a doctor supervises.
What is BMI Prime?
BMI Prime is your BMI divided by the top of the healthy range, 25 (or 23 with Asian cut-offs). A value of 1.0 is the upper limit, so 1.12 means 12% above it.
Why are there different BMI cut-offs for Asian people?
Studies found that many Asian populations develop type 2 diabetes and heart disease at a lower BMI. A 2004 WHO expert consultation therefore suggested extra action points at 23 and 27.5.
Is this medical advice?
No. The results are population estimates for healthy adults. If you have a health condition, are pregnant, or plan a big change in diet, talk to a doctor or registered dietitian first.