BMI Calculator
Enter your height and weight — your BMI and category update live.
How BMI Calculator Works
Body Mass Index (BMI) is a quick screening number that relates your weight to your height, used as a rough indicator of whether your weight falls in a typical range for your height. This calculator works in either metric (cm / kg) or imperial (in / lb) units and updates your BMI and healthy weight range as you type.
Formula & Method
In metric units, BMI is calculated as weight (kg) ÷ height (m)2. In imperial units, this calculator uses the standard conversion 703 × weight (lb) ÷ height (in)2. Your healthy weight range is then found by solving the same formula for weight at the two standard BMI cutoffs, 18.5 and 24.9.
Worked Example
For a height of 170 cm and a weight of 70 kg: BMI = 70 ÷ (1.70 × 1.70) = 70 ÷ 2.89 ≈ 24.2, which falls in the "Normal weight" category. For that same height, the calculator reports a healthy weight range of about 53.5 kg to 72.0 kg.
Frequently Asked Questions
- What do the BMI categories mean?
- This calculator labels a BMI under 18.5 as Underweight, 18.5 to just under 25 as Normal weight, 25 to just under 30 as Overweight, and 30 or above as Obese -- the standard World Health Organization cutoffs for adults.
- Is BMI calculated differently for men and women?
- No -- the BMI formula itself uses only height and weight and does not factor in sex. Some other body-composition measures do account for sex, but standard BMI does not.
- Why does BMI not account for muscle mass?
- BMI only uses height and weight, so it can't distinguish muscle from fat -- a very muscular person can show a high BMI while carrying little body fat. It's best treated as a quick population-level screening tool rather than a precise measure of body composition for any one individual.
- Do the metric and imperial modes give the same result?
- They should be very close. The imperial formula (703 × lb ÷ in²) is a standard conversion of the metric one, so converting the same height and weight between units and switching modes will give matching BMI values, aside from small rounding differences from unit conversion.