The site
About
Who runs this, how the tools are made, and how the site pays for itself.
What this site is
9odo.com is an index of small, single-purpose web tools. There are 7 tools listed today on the front page, plus a flag quiz at /flag-quiz/. Each tool is its own small site published under its own path, so a tool can be fixed, changed or retired without touching the others.
9odo.com is an independent publisher run by a small team. It is not affiliated with any organisation, company or data provider quoted or linked from the individual tools.
How tools are chosen and written
A tool is added when it answers one concrete question that people otherwise settle with a spreadsheet, a calculator or a guess, and when the answer can be shown on the page rather than described in a paragraph. Tools that need medical, legal or financial advice to be safe are not a fit and are left out.
Each tool carries its own explanation: what the number or result means, how it was worked out, where the underlying data comes from, and what the tool deliberately does not claim. Data is taken from published, publicly accessible sources and stated on the tool's pages; values that cannot be traced to a source are not shown as fact. Pages are written for the tool they sit in and are not copied between tools.
What the tools have in common
No accounts and no sign-up are needed to use the calculators and reference tools. Where such a tool takes input, it is processed inside your browser and is not sent to us. The one exception is the flag quiz, which keeps a game record and an optional public leaderboard entry on a server; the details are on the privacy page and the flag quiz's own privacy page.
The site is funded by advertising (Google AdSense), and analytics (Google Analytics) is used to see which pages are useful. The advertising script is loaded on every page, including this one, but this index page does not place an ad unit of its own. Ads on tool pages are labelled and kept out of the first screen, and the tools never ask you to click them.
Reporting a problem
A wrong result matters more than a broken layout. If a tool gives you an answer you believe is incorrect, the useful report names the tool, the exact input, the answer shown and the answer you expected. Corrections are checked against the cited source and, where the tool was wrong, fixed on the page.
Corrections, questions and removal requests: zkfmapf999@gmail.com