What BMI is
Body Mass Index is one very simple piece of arithmetic: your weight divided by the square of your height. The number that falls out of that calculation is used in public-health statistics because it’s easy to collect at scale, and that is its main job.
UnityLife is a lifestyle publication. We aren’t clinicians, and this tool is not a screening, a diagnosis, or a health verdict. It shows you the number. Anything beyond that — whether the number is good, bad, or meaningful for you personally — belongs to your own doctor.
How BMI is calculated
The formula is: BMI = weight (kg) ÷ height (m)². A person who weighs 70 kg and is 1.70 m tall has a BMI of 70 ÷ (1.70 × 1.70) = 24.2. If you work in imperial units, our calculator converts pounds to kilograms (× 0.4536) and feet/inches to centimetres (× 2.54) before applying the same formula.
What BMI does not measure
- Body fat percentage.
- Muscle mass vs fat mass.
- Where body fat is stored (visceral, subcutaneous, etc.).
- Bone density, hydration, or hormonal state.
- Fitness, strength, or cardiovascular health.
- Diet, sleep, stress, or any lifestyle factor.
For these reasons, BMI is widely critiqued as a personal health indicator by researchers and clinicians. It has been shown to mis-represent athletes, people of South Asian, Southeast Asian and East Asian descent, older adults, and many other groups.
If you want a health read, talk to a professional
We deliberately don’t tell you what your BMI “means.” A regulated Canadian clinician — a family doctor, a nurse practitioner, or a registered dietitian — can look at your whole picture (blood work, fitness, history, goals) and give you an actual answer. A website calculator cannot.
Frequently asked questions
What is BMI?
Body Mass Index is a ratio of weight to height squared: BMI = weight (kg) ÷ height (m)². It was developed in the 1830s by a Belgian statistician and is used today as a rough population-level screening signal in public health data. It is not a measure of body fat, fitness, or health, and UnityLife does not present it as one.
How is BMI calculated?
BMI = weight (kg) ÷ height (m)². A 70 kg adult who is 1.70 m tall has a BMI of 70 ÷ (1.70 × 1.70) = 24.2. In imperial units, we convert your inputs to metric (pounds × 0.4536, feet/inches × 2.54) and apply the same formula.
Will this tool tell me if my BMI is healthy?
No. UnityLife is a lifestyle publication, not a medical one, and we deliberately do not categorise your BMI number as "healthy", "overweight" or anything else. Interpreting what a BMI number means for one person belongs to that person’s doctor.
Is BMI actually useful?
At a population level, yes — Health Canada and the WHO use BMI in national statistics. At an individual level it has well-known limitations (it ignores muscle vs fat, fat distribution, age, ethnicity and many other factors) and is increasingly criticised as a personal health indicator. Your clinician has better tools.
Who should not rely on BMI?
BMI has never been validated for children and teens, pregnant or breastfeeding people, competitive athletes with high lean mass, frail older adults, or people with conditions affecting fluid balance. If any of those apply, speak to a clinician before drawing any conclusion from this number.
Does UnityLife store my BMI inputs?
No. Every calculation happens entirely in your browser. Nothing you enter — weight, height, units — is sent to our servers or saved anywhere.
Not medical advice. UnityLife is a Canadian lifestyle publication. This calculator is general information only and is not a substitute for care from a regulated Canadian clinician.