BMI calculator
Enter your weight and height to see your BMI, the adult category and a weight range for your height.
Free · no signup Runs in your browser
How do I calculate my BMI?
BMI is your weight in kilograms divided by your height in metres squared. A person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9. For adults, Health Canada's categories are underweight under 18.5, normal weight 18.5 to 24.9, overweight 25 to 29.9 and obese 30 and over. The calculator works in kilograms and centimetres or in pounds, feet and inches, and shows the weight range that would give a BMI of 18.5 to 24.9 at your height.
What BMI is, and what it is not
Body mass index is a quick way to compare weight with height. It was designed for studying populations, and public-health bodies use it as a screening number because it needs only a scale and a tape measure. Health Canada's guidelines use the same cut-offs for adults aged 18 and over, with the exception of pregnant and lactating women: under 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight and 30 and over is obese. The World Health Organization defines overweight as a BMI of 25 or more and obesity as 30 or more.
BMI has well-known limits. It cannot tell muscle from fat, so a muscular athlete can have a high BMI and little body fat, and an older adult who has lost muscle can have a normal BMI with a high fat share. It says nothing about where fat is carried, and risk is not the same in every ethnic group. Health Canada notes that the system may over- or underestimate risk in very muscular adults. A number in the overweight or obese range is a reason to look at your waist, your habits, your blood pressure and your blood tests with a health professional, not a diagnosis.
It runs in your browser. Nothing you enter is sent anywhere, and there is no sign-up.
Using the weight range
The range shown is simply the weights that would give a BMI between 18.5 and 24.9 at the height you entered, found by multiplying those two BMI values by your height squared. It is a statistical band, not a personal target; the weight that is healthy for you depends on your frame, your muscle, your age and your health. If you are thinking about changing your weight, a family doctor or dietitian can set a goal that suits you, and in Canada a dietitian's advice is available through many provincial health lines at no cost, such as 811 in several provinces.
When to use it
- Getting a quick, standard reading to bring to a health appointment
- Checking the weight range for your height
- Converting a height and weight between metric and imperial first
- Following a trend over time, using the same scale and conditions
Mistakes it helps you avoid
- Treating BMI as a verdict on health.
- Using BMI categories for a child or teen: growth charts are used instead.
- Mixing feet and inches into a decimal (5 ft 10 in is 70 inches, not 5.10 ft).
- Using it during pregnancy, when it does not apply.
The formula
How the answer is worked out.
BMI = weight (kg) ÷ height (m)²pounds and inches: BMI = weight (lb) × 703 ÷ height (in)² (the calculator converts to kg and m first)weight range = 18.5 × height² to 24.9 × height²categories (adults 18+): under 18.5, 18.5–24.9, 25–29.9, 30 and over
The categories are Health Canada's adult body weight classification. The pounds-and-inches version of the formula uses 703, which is 0.45359237 ÷ 0.0254². Results are shown to one decimal place.
Example: 70 kg and 175 cm
An adult weighs 70 kg and is 175 cm tall.
- Height in metres1.75
- Height squared1.75 × 1.75 = 3.0625
- BMI70 ÷ 3.0625 = 22.9
BMI 22.9: normal weight (18.5 to 24.9)
The weight range for 175 cm is 56.7 kg to 76.3 kg.
Terms on this page
- BMI
- Body mass index: weight in kilograms divided by height in metres squared.
- Screening
- A quick check that points to who might need a fuller assessment; it is not a diagnosis.
Common questions
What is a normal BMI?
For adults, Health Canada lists 18.5 to 24.9 as normal weight.
What BMI is overweight?
25 to 29.9 is overweight, and 30 and over is obese, in Health Canada's adult categories.
Does BMI apply to children?
No. The adult categories apply from age 18. Children and teens are assessed on growth charts.
Is BMI accurate for athletes?
Not always. It cannot tell muscle from fat.
Does BMI apply in pregnancy?
No. The Health Canada categories exclude pregnant and lactating women.
Is anything I enter sent to a server?
No. The calculation happens in your browser and nothing you type leaves your device.
Where these numbers come from
- Health Canada — Canadian Guidelines for Body Weight Classification in Adults: questions and answers for the public The adult BMI categories used here: under 18.5, 18.5 to 24.9, 25 to 29.9 and 30 and over; applies to people 18 and older, with the exception of pregnant and lactating women (page modified November 25, 2019).
- World Health Organization — Obesity and overweight (fact sheet) BMI as weight in kilograms divided by height in metres squared; overweight is a BMI of 25 or more and obesity 30 or more.
Last verified 2026-10-26 Rates on this page are checked against the sources above at least once a year, and whenever the governing authority announces a change. Spotted something out of date? Tell us and we will fix it.
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