BMI Calculator
Why this tool?
Check BMI with unit presets, see the healthy weight range for your height, approximate body fat using the Deurenberg formula, and estimate maintenance calories (TDEE) with Mifflin-St Jeor. Everything runs locally.
Useful for quick fitness check-ins, onboarding flows, or coaching notes without sharing data.
How to use it
Select metric or imperial units, enter height and weight, and click Calculate. The page converts as needed, reports BMI with category, and fills the meter so you see your position visually. Provide age for body fat estimation and waist (optional) for added context in coaching notes. Switch units at any time to view the same numbers in kg/cm or lb/in without retyping.
The healthy range panel shows the target weight span for a BMI of 18.5–24.9 in both kg and lb, giving you clear goals. The details panel summarizes estimated body fat and maintenance calories using light-activity TDEE so you can plan next steps or discuss with a professional.
Who benefits
Fitness coaches preparing quick assessments, product teams building onboarding flows for health apps, clinicians offering general guidance (not medical advice), and individuals checking progress all gain a fast reference. Researchers and students can demonstrate BMI limitations while still presenting consistent calculations.
Support teams for wellness products can troubleshoot user reports by replicating entries exactly, thanks to explicit unit toggles and deterministic formulas. Because everything is client-side, it is safe to use in privacy-sensitive environments.
Implementation details
BMI is computed from metric values; imperial inputs are converted on the fly. Body fat uses the Deurenberg approximation (1.2×BMI + 0.23×age − 10.8×sex − 5.4), and TDEE uses the Mifflin-St Jeor equation with a light-activity multiplier. These are estimates, not medical diagnostics.
No data is sent or stored. All calculations run instantly in the browser with no third-party libraries, keeping performance high on mobile and low-power devices. Reset returns defaults for quick repeated checks during coaching sessions or user support.