About Otoolia
Otoolia is an independent website offering 56 free online tools, in French and English, to learn, teach, create, train and get organised. No account is needed and the tools run right in your browser.
Who is behind the site?
Otoolia is designed, built and maintained by Erwan Hautot, a mathematics teacher and the site's publisher (see the legal notice). These tools were created with one simple aim: to make your life easier, by making everyday, study and work tasks quick and accessible to everyone, with no account or software to install. There is no agency and no bought content: every tool and every text is written and reviewed before publication. For questions, corrections or ideas: contact@otoolia.com.
Why these tools?
Each tool starts from a real need: preparing a physics or chemistry lab, building an oral-exam timetable, revising with Anki flashcards, tuning a guitar, estimating take-home pay or a mortgage payment, planning a mountain hike, printing a packing list… The aim is to beat existing tools on at least one point: more complete, clearer, printable, exportable, or simply free of sign-ups and intrusive ads.
How the tools are built and checked
- Published methods. Calculations rely on identified sources: official tax and contribution scales, published formulas and algorithms (Easter computus, ephemerides, Flesch readability, diving formulas…). Sources and limits are stated on each tool's page.
- Test cases. Before release, results are compared with reference values and other calculators (for example 252 working days in metropolitan France in 2026, unit conversions, the year's tax brackets).
- A look at what exists. The main similar tools are reviewed to keep their good ideas and fill their gaps (export, printing, edge cases).
- A page that explains. Each tool comes with a guide: how to use it, how it calculates, worked examples, common mistakes and frequent questions.
- Dated updates. The last update date is shown at the bottom of every page; yearly scales are refreshed every year.
Your data stays with you
Files (PDFs, images), texts, lists and calculations are processed in your browser: they are not sent to a server. What you save (lists, settings, card decks) is kept in your device's local storage and can be exported. Generated passwords are never stored. Analytics and advertising are only enabled with your consent (details).
Free, funded by discreet advertising
Otoolia is free and will stay free. To cover hosting and development time, the site may show ads, placed so that they never get in the way of the tools.
Tools by topic
- 🎵 Music — 5 tools : Tune, practise, understand theory.
- 🗂️ Anki & memory — 3 tools : Create flashcards and study them.
- 🎓 Education — 17 tools : Exercises, worksheets and classroom tools.
- 🤖 Artificial intelligence — 2 tools : Prompts, assistants and AI experiments.
- 🌊 Sport & outdoors — 7 tools : Running, hiking, cycling, diving, interval training, tournaments, sun and moon.
- 💶 Money & work — 9 tools : Salary, budget and everyday calculations, with up-to-date rates.
- 🩺 Health & wellbeing — 2 tools : Health indicators computed in your browser, with no data sent.
- 🧰 Utilities — 11 tools : Handy everyday tools.
What's new
- — 📟 Graphing calculator (new tool)
- — 🪑 Seating plan (new tool)
- — 💸 Expense splitter (new tool)
- — ➗ Percentage calculator (new tool)
- — 🖼️ Image compressor (update)
- — 🏃 Pace calculator (new tool)
- — 🥾 Hiking time calculator (new tool)
- — 🌅 Sun and moon (new tool)
- — 🚴 Bike gears and tyre pressure (new tool)
- — ⏱️ Interval timer (new tool)
- — 🏆 Tournament generator (new tool)
- — 📏 Unit converter (new tool)
- — 📅 Date and working-day calculator (new tool)
- — 🔑 Password generator (new tool)
- — 🔤 Word counter and typography (new tool)
Report a mistake, suggest an idea
A result looks wrong, a case is missing, a feature would help? Use the “Got an idea?” button on the pages, or write to contact@otoolia.com. Fixes are made quickly and the most requested ideas become new tools.