BMI Calculator
Calculate your Body Mass Index and see which weight category you fall into.
Try an example
24.2
Healthy weightAbout this calculator
How This BMI Calculator Works
Enter your height and weight — in metric or imperial units — and the calculator returns your Body Mass Index along with which standard weight category it falls into.
Worked Example
At 170 cm and 70 kg, BMI = 70 ÷ (1.70 × 1.70) = 24.2 — inside the healthy weight range.
The Formula
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lb) ÷ height (in)² — the 703 factor puts the result on the same scale as the metric formula.
BMI Categories
- Below 18.5 — underweight
- 18.5–24.9 — healthy weight
- 25–29.9 — overweight
- 30 and above — obesity
Why BMI Has Real Limitations
BMI doesn't distinguish muscle from fat, so athletes and very muscular people often score higher without carrying excess body fat. It also doesn't account for age, sex, or where fat is distributed on the body — two people with identical BMI can have very different body compositions and health profiles. Treat it as a fast screening tool for population-level trends, not an individual diagnosis. The Body Fat Calculator and Ideal Weight Calculator add context BMI alone can't provide.
Worked example
At 170 cm and 70 kg, BMI = 70 ÷ (1.70 × 1.70) = 24.2 — inside the healthy weight range (18.5–24.9).
Frequently asked questions
What do the BMI categories mean?
Under 18.5 is underweight, 18.5–24.9 is a healthy weight, 25–29.9 is overweight, and 30+ is considered obesity — these are the standard adult thresholds used by most health authorities.
Is BMI accurate for everyone?
No. It doesn't distinguish muscle from fat, so athletes and very muscular people often score higher without excess body fat. It also doesn't account for age, sex, or where fat is distributed.
What's the formula in imperial units?
BMI = 703 × weight (lb) ÷ height (in)². The 703 factor puts the result on the same scale as the metric kg/m² formula.
Should I use BMI alone to judge my health?
Treat it as a quick screening tool, not a diagnosis — waist circumference, body fat percentage, and a conversation with a doctor give a fuller picture.