BMI Calculator. Calculate adult BMI from metric or imperial height and weight. See CDC screening categories, formula steps, and limitations without treating BMI as a diagnosis.
Choose your path
Calculate adult BMI consistently across metric and imperial units while explaining screening limits and avoiding unsupported individualized health judgments.
Convert height/weight into BMI and a clearly sourced adult category.
Enter metric values, inspect equation/category, and compare the screening range with personal context.
Gets reproducible arithmetic and understands BMI is a population screening measure, not a diagnosis.
Get the same physical result from pounds and feet/inches.
Switch units without changing the represented body measurements and compare BMI/healthy-weight output.
Unit switching preserves the physical values within rounding tolerance.
Avoid a false promise that one BMI target is individually healthy.
Review age/sport/pregnancy/body-composition caveats and extreme-result guidance.
Sees source-qualified general categories and seeks individualized advice when BMI is not an appropriate standalone measure.
This tool is part of these guided projects. Each project provides step-by-step instructions with checklists and all the tools you need in one place.
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BMI is calculated by dividing weight by height squared. Use metric (kg/m²) or imperial units with the 703 conversion factor.
Metric: BMI = weight(kg) / height(m)² | Imperial: BMI = (weight(lbs) × 703) / height(inches)²Underweight (<18.5), healthy weight screening category (18.5–24.9), overweight (25–29.9), and obesity (≥30). CDC uses these standard cut points for adults age 20 and older, regardless of age, sex, or race and ethnicity.
BMI is a screening measure. Individual assessment may also consider body composition, waist size, history, examination, behaviors, and laboratory findings. People under 20 require BMI-for-age percentiles.
Source: CDC BMI FAQ
Updated: August 2026
A routine health screening for an adult at 70kg and 175cm to check weight category.
→ BMI: 22.9 — Normal weight
Athletes may have a high BMI due to muscle mass rather than excess body fat. BMI alone doesn't distinguish muscle from fat.
→ BMI: 27.8 — Overweight screening category; BMI alone cannot determine body fat or health
A gym member records height and weight in the BMI Calculator to establish a baseline BMI and revisits monthly to track progress toward a goal.
BMI doesn't distinguish between muscle and fat. Consider body fat percentage, waist circumference, fitness level, and other health markers for a complete picture.
Children need age-and-sex-specific BMI percentile charts (CDC/WHO growth charts). Adult BMI thresholds do not apply to pediatric populations.
Body Mass Index (BMI) is a height-and-weight screening measure for adults age 20 and older. It does not directly measure body fat or diagnose individual health.