About & Methodology

A collection of health and fitness calculators — BMI, daily calories (TDEE), body fat, protein intake, pregnancy due date, and more to come — that are free, private, and require no sign-up. Calculations run entirely in your browser; nothing you enter leaves your device. The goal is a calm, accurate, measurement-instrument feel rather than a busy wellness blog.

Most calculator sites give you a number and nothing else. We show the evidence behind it. On every calculator you'll find:

• The formula's source — the organization and reference the calculation is based on.
• A confidence level — an honest signal of how precise the estimate is, from a well-validated screen to an estimate with wide individual variation.
• A last-reviewed date and version — so you know the figure isn't stale, and changes are tracked over time.
• Plain-language limitations — who the tool is most and least accurate for, and when to seek a professional instead.

Each calculator's math lives in an isolated, testable module. We take the formula, cutoffs, and citations from published public-health and scientific sources — for example the World Health Organization, U.S. CDC, National Institutes of Health, the American College of Obstetricians and Gynecologists, and peer-reviewed literature — rather than deriving or guessing values ourselves.

Before a calculator ships, its formula is unit-tested against the known reference values from its cited source. Formulas are version-controlled: if a value or cutoff changes, that's a tracked change with a version bump, not a silent edit. Where the evidence genuinely differs by population — such as the WHO's separate BMI cutoffs for Asian populations — we apply the appropriate regional standard and let you compare.

• We don't invent medical-reviewer credentials. Our content is compiled from cited sources; we do not claim it has been reviewed by a named clinician unless and until that review genuinely happens.
• We don't present estimates as diagnoses. Health results use language like "estimate," "typical range," and "may indicate" — never diagnostic claims.
• We don't hide behind logins or harvest your data to monetize it (see our Privacy Policy).
• We don't pad the catalog with tools we haven't actually built — the homepage lists what's genuinely live.

HealthCalcNow is an informational and educational tool, not a medical service, and it does not replace professional advice. A calculator can screen, estimate, and inform a conversation — it cannot examine you, know your history, or diagnose a condition. For anything that matters to your health, talk to a qualified healthcare provider.

Found a figure that looks off, or a source that should be updated? We take accuracy seriously and would rather hear about it. A contact channel for corrections will be listed here; in the meantime, treat every result as a starting point and cross-check anything that affects a real decision.