Why BMI calculators can give different results
Check the units, how height was entered, the formula and the rounding convention before comparing results. A change in a displayed number is not by itself a change in health. Keep the calculation separate from personal treatment or weight goals.
The short answer
Check the units, how height was entered, the formula and the rounding convention before comparing results. A change in a displayed number is not by itself a change in health. Keep the calculation separate from personal treatment or weight goals. Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion.
How we calculate
Check the units, how height was entered, the formula and the rounding convention before comparing results. A change in a displayed number is not by itself a change in health. Keep the calculation separate from personal treatment or weight goals.
Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 in = 2.54 cm. Five feet nine inches is 69 inches, not 5.9 feet.
Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion.
A reproducible calculation
Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 in = 2.54 cm. Five feet nine inches is 69 inches, not 5.9 feet.
BMI = kg / m²
150 × (0.45359237 / 0.0254²) / 69² = 22.1509004
150 × 703 / 69² = 22.1487083| How we calculate | Value |
|---|---|
| Imperial (lbs/ft-in); SI | 22.1509004 |
| Imperial (lbs/ft-in); ×703 | 22.1487083 |
Practical checks before interpreting BMI
Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion.
| Value | Category |
|---|---|
| 24.96 | Normal |
| 25.04 | Overweight |
Screening scope
Adult (20+), not pregnant. For ages 2–19, use a validated BMI-for-age calculator. This tool shows adult ranges only.
BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy.
The standard adult BMI formula is the same for women and men. The same BMI does not establish the same body composition or personal health risk.
This explanation checks the method and arithmetic. It does not claim an independent medical review. Personal interpretation requires context and an appropriate healthcare professional.
Sources
BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy. This explanation checks the method and arithmetic. It does not claim an independent medical review. Personal interpretation requires context and an appropriate healthcare professional.
Sources below are in English.
- CDC: BMI
Body mass index (BMI) is weight in kilograms divided by height in metres squared. It is one screening measure, not a diagnosis or a direct measurement of body fat.
- CDC: BMI 20+
Adult (20+), not pregnant. For ages 2–19, use a validated BMI-for-age calculator. This tool shows adult ranges only.
- NIST: SI
Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 in = 2.54 cm. Five feet nine inches is 69 inches, not 5.9 feet.
Kymata Labs LLC · Contact and corrections.