BMI Calculator
Calculate Body Mass Index (BMI) for adults using Metric (cm/kg) or US Customary (ft/in/lb) units.
Calculate BMI using height in centimeters and weight in kilograms.
BMI category: Healthy Weight
How to Calculate Body Mass Index (BMI)
Standard metric and US customary formulas with adult weight category thresholds.
Metric BMI Formula
Body Mass Index (expressed in kg/m²) is calculated by dividing body weight in kilograms by the square of height in meters.
When to use: Use when height is measured in centimeters (cm) and weight in kilograms (kg).
US Customary BMI Formula
When using pounds and inches, total height in inches is squared and divided into weight in pounds, then multiplied by the conversion factor 703 (which equates lb/in² to kg/m²).
When to use: Use when height is measured in feet and inches (ft/in) and weight in pounds (lb).
Practical Calculation Examples
Real-world scenarios illustrating step-by-step numbers, inputs, and verified outputs.
Metric Adult Example (Healthy Weight)
An adult with height 170 cm and weight 70 kg.
US Customary Adult Example (Healthy Weight)
An adult with height 5 ft 7 in and weight 154 lb.
Metric Adult Example (Overweight)
An adult with height 175 cm and weight 85 kg.
Metric Adult Example (Obesity Class 1)
An adult with height 165 cm and weight 90 kg.
Frequently Asked Questions
Common questions about BMI calculation, adult categories, units, and healthy weight ranges.
How is BMI calculated?
For metric units, BMI is calculated by dividing weight in kilograms by the square of height in meters: BMI = weight (kg) ÷ (height (m))². For US customary units, BMI is calculated as: BMI = (weight (lb) ÷ (height (in))²) × 703.
What information do I need to calculate BMI?
To calculate your BMI, you need your current height (in centimeters or feet and inches), your body weight (in kilograms or pounds), and your age. Adults aged 20 and older are evaluated against standard adult weight categories.
Can I calculate BMI using height in feet and weight in kilograms?
YourCalculate provides dedicated Metric (cm and kg) and US Customary (ft/in and lb) modes. If your height is in feet and your weight is in kilograms, convert your height to centimeters (1 foot = 30.48 cm, 1 inch = 2.54 cm) to use Metric mode, or convert your weight to pounds (1 kg ≈ 2.20462 lb) to use US Customary mode.
Does BMI directly measure body fat?
No. BMI is an anthropometric screening ratio based solely on height and weight. It does not directly measure body fat percentage, lean muscle mass, bone density, or adipose tissue distribution. Two individuals with the same BMI may have substantially different body compositions.
Does age or sex affect how BMI is interpreted?
Standard CDC and WHO adult BMI categories (18.5 to 24.9 as healthy weight) apply equally across adult men and women aged 20 and older. However, because body composition naturally varies by biological sex and changes with aging, BMI should be interpreted as an initial screening indicator rather than a comprehensive diagnostic measure.
What BMI categories are used for adults?
According to standard CDC and WHO guidelines for adults (ages 20+): Underweight is BMI < 18.5, Healthy Weight is 18.5 ≤ BMI < 25.0, Overweight is 25.0 ≤ BMI < 30.0, and Obesity is BMI ≥ 30.0 (subdivided into Class 1: 30.0–34.9, Class 2: 35.0–39.9, and Class 3: ≥ 40.0).
Does this BMI calculator work for children and teenagers?
No. This calculator is designed specifically for adults aged 20 and older. For children and adolescents (ages 2–19), BMI must be evaluated using pediatric BMI-for-age percentiles and sex-specific growth charts rather than fixed adult cutoff thresholds.
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