BMI Calculator
Work out body mass index from height and weight, in metric or imperial units, and see where that places you on the World Health Organization scale for adults. The maths happens in this browser tab — nothing is sent anywhere.
Measurements
Result
Private by design. This page has no backend. Your measurements are processed by JavaScript on your own device and never leave this page.
What BMI is
Body mass index relates weight to height: weight in kilograms divided by the
square of height in metres. It is a screening tool, not a diagnosis — it was
designed for populations, and it does not distinguish muscle from fat, or account for
age, frame or where weight is carried. Two people with identical BMI can have very
different body composition.
The categories
This page uses the World Health Organization cut-offs for adults:
Under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is obese. The healthy range shown for your height is the weight that would sit your BMI between 18.5 and 25.
How the units are handled
Metric is used for the formula as-is. Imperial is converted first — pounds to
kilograms (lb × 0.45359237) and feet and inches to metres
(total inches × 0.0254) — and the same formula runs on the result. The
conversion constants are exact, so switching units for the same body gives the same
BMI to a rounding error.
Reading the answer
The headline number is rounded to one decimal place. The category and the healthy weight range for your height appear alongside it, and the range is quoted in the unit system you chose.
What to do about the number
Treat BMI as a flag, not a verdict. If it is surprising either way, talk to a health professional about what it means for you. This page is a calculator, not medical advice.
Common uses
A quick sense of whether weight is in a typical range, tracking changes in the index over time (which mirrors weight changes when height is fixed), and paperwork that asks for a BMI alongside weight and height.
How to use the BMI Calculator
- Choose metric or imperial units.
- Enter your height and weight.
- Read your BMI, its WHO category and a healthy weight range for your height.
Frequently asked questions
Is BMI accurate for everyone?
No. BMI is a population screening tool and does not distinguish muscle from fat or account for age, frame or body composition.
Which categories does it use?
The World Health Organization adult cut-offs: under 18.5, 18.5 to 24.9, 25 to 29.9, and 30 or above.
Does switching units change the result?
No. Imperial values are converted with exact constants, so the same body gives the same BMI.