Frequently Asked Questions

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.

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. 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.

Adults 20+. Normal: 18.5 ≤ BMI < 25. 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.

For ages 2–19, use a validated BMI-for-age calculator. This tool shows adult ranges only. Adults 20+.

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. Optional circumference estimate. It is not a direct body-fat measurement; incomplete or implausible measurements show no estimate.

BMI Prime is the ratio of your BMI to 25, which is the upper limit of the WHO normal range. A BMI Prime of 1.0 means you are at the boundary between normal weight and overweight. Below 1.0 means you are in the normal or underweight range. Above 1.0 means you are overweight or obese. For example, a BMI of 22.5 gives a BMI Prime of 0.90 (22.5 / 25). BMI Prime is useful for quickly seeing how far you are from the normal-overweight threshold.

Ponderal Index = kg/m³. 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.

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Yes, BMI Calc Now is completely free. No sign-up required, no hidden fees, no premium tier. All 20 language versions are free and fully functional.