BMI Calculator — Frequently Asked Questions

BMI is a simple ratio of weight to height (kg/m²) used to screen for underweight, healthy weight, overweight and obesity. It doesn't measure body fat directly but is useful for population-level screening.

BMI = weight (kg) ÷ height (m)². If using Imperial units, we convert lb and ft/in to metric before calculating. The app handles that conversion automatically.

BMI Prime expresses your BMI as a ratio of the upper healthy BMI (usually 25). A BMI Prime of 1.0 equals BMI 25; higher values indicate how far above that threshold you are.

These are algorithmic estimates intended for education and tracking. They are not clinical diagnostics. For medical concerns or precise testing, consult a healthcare professional and clinical tests (DEXA, bloodwork, etc.).

They use accepted formulas (Navy, predictive BMR equations). Results are reasonable estimates but can differ from clinical measures. Use them as guidance, not definitive medical values.

Inputs are used to compute results. We don't store personal measurement data permanently by default. Some sessions may call a server API; consult the privacy policy for details and options to clear data.

Yes. Toggle Metric or Imperial on the form. The site converts Imperial inputs (lb, ft/in) to metric for internal calculations automatically.

Waist, hip and neck measurements enable the Navy body-fat estimate and improve risk stratification (waist-to-hip ratio). These give more context than BMI alone.