Making trustworthy health insight accessible to everyone, everywhere, for free.
HydraFit.online was created with a simple goal: to give anyone, anywhere, free and instant access to the same kinds of health calculations used by doctors, dietitians, and personal trainers — without paywalls, invasive sign-ups, or confusing jargon.
We believe that understanding your own body shouldn't require an appointment, a subscription, or a spreadsheet. Whether you're tracking your fitness progress, planning meals, preparing for a workout program, or simply curious about your numbers, HydraFit puts clear, science-based answers at your fingertips.
HydraFit hosts a growing library of 15+ specialised calculators spanning body composition, nutrition, fitness performance, sleep, vitals, and women's health. Every tool is built around established, peer-reviewed formulas — including the Mifflin-St Jeor equation, the U.S. Navy body fat method, and WHO waist-to-hip ratio guidelines — so you can trust the numbers behind the results.
| Accuracy | Every formula is sourced from recognised clinical or exercise-science literature, not guesswork. |
|---|---|
| Privacy | All calculations run locally in your browser. We do not collect, store, or transmit the personal figures you enter into our tools. |
| Accessibility | Every tool is free, ad-light, and designed to work on any device — no downloads, accounts, or subscriptions required. |
| Transparency | We clearly explain the formula and methodology behind every calculator, and we are upfront about the limitations of self-assessment tools. |
HydraFit is an independent digital health information project built and maintained by a small team passionate about fitness, nutrition science, and accessible web design. We are not a medical practice, and none of our content should be taken as individualized medical advice — see our Medical Disclaimer for full details.
Have feedback, found a bug, or want to suggest a new calculator? We'd love to hear from you — visit our Contact page to reach out.