→ Something people say
"It's just crossed out: a number that decides for me changed to: one number, and I'll know what it leaves out."
BMI calculator, metric or imperial, with what the number leaves out.
Work out your body mass index (BMI) in metric or imperial units. This BMI calculator for adults in Canada uses Health Canada's adult ranges, tells you what your number means and, just as plainly, what it leaves out. It runs in your browser: nothing you type is stored or sent anywhere.
The real answer
BMI is a quick screening number, not a verdict on your health.
BMI is your weight divided by your height squared. Health Canada calls it a useful indicator of weight-related health risk but not a direct measure of body fat, and only one part of a fuller health assessment. It can't see your history, your labs or how you feel. A clinician can.
- Your height and weightyou
- The number and what it meansthis calculator
- The whole pictureyour NP
Health Canada's adult BMI ranges, in one table.
For adults 18 and over, not during pregnancy or breastfeeding. For people 65 and over, Health Canada notes the "normal" range may start slightly above 18.5.
| BMI | Health Canada classification |
|---|---|
| Under 18.5 | Underweight |
| 18.5 to 24.9 | Normal weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity class I |
| 35.0 to 39.9 | Obesity class II |
| 40.0 and over | Obesity class III |
BMI can't see muscle, history or how you feel.
Health Canada says BMI may underestimate or overestimate health risk for some people: young adults who haven't finished growing, people with very lean or very muscular builds, adults over 65 and some ethnic and racial groups. Canada's adult obesity guideline adds that BMI doesn't show body composition, where fat sits or whether it's affecting your health, and asks clinicians to use ethnicity-specific cut-offs and measures like waist size alongside it. That's why the number is a starting point for a conversation, never the end of one.
Prescription treatment is generally considered at 30, or 27 with a weight-related condition.
Prescription treatment is generally considered for adults with a BMI of 30 or more, or 27 or more with a weight-related health condition. Your clinician makes the final decision. This follows Canada's adult obesity clinical practice guideline, and it's a guide to whether an assessment is worthwhile, never a promise of treatment. Sometimes the right first step is something else.
The calculator and the program both have limits.
The calculator isn't meant for anyone under 18, or during pregnancy or breastfeeding. The program isn't for anyone under 18; anyone pregnant, breastfeeding or planning a pregnancy; or anyone outside Ontario at the time of their visits.
No: adults use the same BMI ranges, whatever their sex.
Health Canada's adult BMI table is the same for women and men. Waist size is where the lines differ: Health Canada links a higher health risk to a waist of 88 cm (35 in) or more for women and 102 cm (40 in) or more for men. Your clinician looks at the whole picture, not one measurement.
Health Canada calls 18.5 to 24.9 the normal weight range for adults.
That range is a population guide. Health is more than one number, and a healthy BMI for you depends on your build, your age, your background and your health, which is exactly what an assessment looks at.
About BMI.
How do I work out my BMI?
Divide your weight in kilograms by your height in metres squared. In imperial, multiply your weight in pounds by 703, then divide by your height in inches squared. The calculator above does it for you.
Does this calculator save or send my numbers?
No. It runs in your browser, and nothing you type is stored or sent anywhere.
What does a BMI of 30 mean?
It's the start of Health Canada's obesity range for adults. It's also the point where prescription treatment is generally considered, as a guide; your clinician makes the final decision.
What does a BMI of 27 mean?
It's in Health Canada's overweight range for adults. Prescription treatment is generally considered from 27 only when there's also a weight-related health condition, and your clinician makes the final decision.
Can I use BMI if I'm pregnant or under 18?
No. Health Canada's adult classification isn't meant for anyone under 18 or during pregnancy or breastfeeding.
Does a high BMI mean I need treatment?
No. BMI is a screening number, not a diagnosis. An assessment looks at your history, labs and goals, and your clinician decides with you what, if anything, makes sense. Is this for me?
→ Your turn
An assessment may be worthwhile.
If your number, your health or your history has you wondering, the next step is a person, not another number. Get started in your own time, and a Nurse Practitioner in Ontario looks at the whole picture with you. Your clinician decides what, if anything, comes next.