Sourced calculator and guide
How do you calculate BMI?
BMI stands for body mass index. Calculate it from measured weight and height; the number alone does not measure body fat or diagnose health.
Calculate your estimate
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Estimate: 22.9 kg/m²
Arithmetic BMI only. This is neither body fat percentage nor a diagnosis; no adult category is applied to a child.
Worked examples from the same calculator
Only the final output is rounded using decimal half-up rules.
| Input scenario | Estimate |
|---|---|
| Metric example | 22.9 kg/m² |
| US example | 22.7 kg/m² |
| Second metric example | 24.7 kg/m² |
Formula of BMI (body mass index)
Metric BMI = kg ÷ m², or kg ÷ cm² × 10,000. US customary BMI = lb ÷ in² × 703. Height must be greater than zero. Enter total inches for US height; 5 feet 9 inches is 69 inches. The CDC’s 703 factor is a rounded customary-unit factor, so US and exact metric conversions may differ slightly.
Adult BMI and BMI for children
The CDC formula page directs adults 20 and older to its adult calculator, and children ages 2 through 19 to its child and teen calculator. Children need age- and sex-specific BMI percentiles; an adult cutoff must not be applied to them. This tool gives the number only, with no percentile, category or diagnosis.
How to measure BMI
Measure height and weight accurately, then use one consistent unit system. BMI is calculated rather than measured directly. It cannot distinguish fat from muscle or describe fat distribution; personal health assessment needs more context.
Source formulas and scope
CDC metric formula: BMI = weight (kg) / [height (m)]². CDC US customary formula (superscript typography retained):
BMI = weight (lb) / [height (in)]² x 703
The US factor 703 is used directly; it is not replaced by the exact metric conversion factor. This number-only tool is not an adult or child assessment. For interpretation, see CDC: About BMI and the age-specific calculators linked in the formula source.
Questions and answers
What does BMI stand for?
Body mass index: a weight-to-height-squared calculation. It is not a direct measurement of body fat.
How to do BMI with metric measurements?
Divide weight in kilograms by height in meters squared. With centimeters, divide kilograms by centimeters twice, then multiply by 10,000.
How do I measure BMI in pounds?
Use measured pounds and total height in inches. Divide pounds by inches squared and multiply by 703. A height of zero is invalid.
Sources
Reviewed October 29, 2026. Original formulas are quoted above; derived scenario arithmetic is identified separately.