Free online calculator · Health
BMI Calculator
Calculate body mass index using height and weight. BMI is a screening metric and is not a medical diagnosis.
Formula • Worked example • Interpretation
Understand adult Body Mass Index (BMI)
BMI is a weight-for-height screening measure used for adults. It is useful for population-level comparisons but cannot directly measure body fat, fitness, or health.
Calculation method
BMI = weight in kilograms ÷ (height in meters)². Using pounds and inches: BMI = 703 × weight(lb) ÷ height(in)².
Worked example
An adult who weighs 180 lb and is 70 inches tall has BMI ≈ 25.8.
What your result means
Common adult screening categories are below 18.5, 18.5–24.9, 25.0–29.9, and 30.0 or higher. These categories are not diagnoses or an assessment of individual health.
Tips for better calculations
Enter total height accurately; an inch of error changes BMI. Compare trends over time rather than relying on a single number.
Assumptions and limitations
Not intended to interpret children’s BMI using adult cutoffs, nor to estimate body composition in pregnancy, elite sport, or individuals with atypical muscle mass. Speak with a clinician for personal interpretation.
Additional reference: CDC — Adult BMI
SiCalcs tools provide estimates and educational calculations; they do not replace professional financial, medical, tax, or legal advice.