Calculate adult BMI from metric or imperial height and weight. See CDC screening categories, formula steps, and limitations without treating BMI as a diagnosis.
A quick decision brief for this specific tool
Adult height and weight in metric or imperial units; age is limited to the adult 20+ scope and sex does not change the formula
BMI, one of four CDC adult screening categories, the weight range corresponding to BMI 18.5–24.9, BMI Prime, and Ponderal Index
Weight in kilograms divided by squared height in meters, classified at the CDC adult cut points of 18.5, 25, and 30
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.
Formula: 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.