Small tools that do one thing
Pick one to open it. The calculators and reference tools need no account and run in your browser.
- Size vs Put any two things side by side at the same scale
- Eat wheel Spin, race or drop a ball to pick what to eat
- Pop vs Compare the population of two countries, 1960 to 2050
- Flag finder Find a flag by its colours and symbols
- Word finder Find words from letters, patterns and Wordle clues
- Time gap Find a meeting time that works in every city
- Food vs Compare foods side by side, and raw against cooked
What each tool does
- Size vs Put any two things side by side at the same scale
Takes any two of 86 animals, buildings, mountains, vehicles and planets and stands them on one baseline at the same scale, with the ratio, the gap and how many of the smaller stack to the larger.
For anyone who has read two sizes in a table and still cannot picture them — a student, a presenter, someone settling an argument.
It compares linear size only, from a curated list rather than every animal or building. Nothing you pick is sent anywhere.
- Eat wheel Spin, race or drop a ball to pick what to eat
A wheel of twelve kinds of food, a wheel of dishes for each, and 3D marble, duck, horse, car, plinko and battle games that pick from a list you type.
For whoever is stuck on what to eat tonight, or has to pick one name from a list without an argument.
It gives no nutrition advice and knows nothing about allergies. Your list stays in your browser.
- Pop vs Compare the population of two countries, 1960 to 2050
Takes any two of 217 countries and areas and draws their populations as crowds of dots at the same scale, with a year slider from 1960 to 2050, the ratio, the gap and the year one passes the other.
For anyone who has read two population figures in a table and still cannot picture them — a student, a presenter, someone following the news.
It compares total population only, from World Bank estimates and projections. Projections continue current trends and are not forecasts of events. Nothing you pick is sent anywhere.
- Flag finder Find a flag by its colours and symbols
Tick the colours a flag contains and the symbols on it — a star, a crescent, a cross — and the grid narrows to the national flags that have all of them, out of 196.
For anyone who has seen a flag and cannot name it, or wants every flag with a star or red and white — a quiz writer, a teacher, a curious traveller.
It labels colours from images and symbols by hand, so a flag can be mislabelled. It includes UN member and observer states and Kosovo, not territories or historical flags. Nothing you pick is sent anywhere.
- Word finder Find words from letters, patterns and Wordle clues
Type the letters you hold, a pattern like c?t, or your Wordle guesses with their colours, and it lists the words that fit — by length and score — and suggests the next guess.
For anyone stuck on a word game, a crossword or a Wordle row — a player, a puzzle setter, a teacher making word lists.
It uses the public-domain ENABLE word list, so some newer or very common words are missing and some obscure ones are included. It is not affiliated with any word game. Nothing you type is sent anywhere.
- Time gap Find a meeting time that works in every city
Stack two to five cities' days as 24-hour bars, move the clock, and see when everyone is inside working hours — with daylight-saving shifts handled for the date you pick.
For anyone scheduling across time zones — a remote team lead, a freelancer with overseas clients, someone calling family abroad.
It treats Saturday and Sunday as the weekend and does not know public holidays. Cities come from a list of about 250 larger ones. Nothing you pick is sent anywhere.
- Food vs Compare foods side by side, and raw against cooked
Pick two or three foods and see 15 nutrients as paired bars per 100 g, per serving or per 100 kcal — or turn a raw weight into the cooked weight with USDA-measured yields.
For anyone weighing two foods or logging meat by raw or cooked weight — a home cook, someone counting macros, a student.
It shows amounts, not health advice, and uses USDA SR Legacy values for about 486 common foods. Yields exist only for the cuts USDA measured. Nothing you pick is sent anywhere.
Also on this site: a game
Flag Quiz is a timed quiz where you name countries from their flags, with a practice mode and a public leaderboard. Unlike the tools above it runs a small server to check scores; see its privacy page for exactly what it keeps. It is not for learning geography in depth, and it does not need an account.
What this is
9odo.com is a small collection of web tools, each built to answer one question well. The address of each
tool is 9odo.com/ plus its name — there is no deeper nesting and no second domain to
remember. Most of them are calculators, comparison tables and reference lookups; one, the flag quiz, is a
game. They are written and maintained by the same small team, which is why they share a layout, a privacy
policy and a way of explaining themselves.
Nothing here is a news feed or a blog. If a page exists, it exists because someone searches for exactly that comparison, conversion or answer, and the page is meant to give it in under a minute and then explain how the answer was reached, so you can decide whether to trust it.
How to choose a tool
Start from the question you have, not from the name. If you want to see how big one thing is next to another — two animals, two buildings, two planets — open a comparison tool and pick both sides. If you want a number for a recipe, a schedule or a time zone, open the calculator that names that quantity. If you simply want to practise recognising flags, use the quiz. The cards at the top of this page give a one-line promise; the list under “What each tool does” says who the tool is for and, just as usefully, what it will not do for you.
Each entry in that list also gives direct links into the tool: usually a front page and two or three of its most useful inner pages. Use those when you already know what you are after. Tools with many generated pages, such as the comparison tool, are organised by category so you can browse rather than guess a name.
How the paths work
The first path segment names the tool. /{tool}/ is its front page, and anything
below it belongs to that tool — its guides, its generated pages, its about page. A bookmark therefore
keeps pointing at the same thing even if the index changes. A path that is not part of one of the listed
tools does not exist on this site and returns a 404 page that links back here.
Tools are added to the index when they are deployed, not before, and are removed from it if they are retired. That is why there are no “coming soon” entries on this page: every card opens something that works today.
What the tools have in common
The calculators and reference tools need no account and no sign-up. What you type is handled by the page in your browser and is not sent to a server of ours. Some tools remember your own settings in your browser's local storage so they can show them again; clearing site data removes them.
One tool works differently. The flag quiz, at /flag-quiz/, runs a small server so that scores can be checked and a public leaderboard can exist. It keeps a record of each game, lets you submit a nickname with a score, and stores a one-way code derived from your IP address to limit automated play. Its own privacy page describes exactly what is kept and for how long.
The site is paid for by advertising (Google AdSense) and uses Google Analytics 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. On tool pages, ads are labelled, kept out of the first screen, and the pages never ask you to click them. The privacy page lists the cookies this involves and how to opt out.
Where the data and wording come from
Every tool carries its own explanation: what the result means, how it was worked out, where the underlying numbers come from and what the tool deliberately does not claim. Figures are taken from published, publicly accessible sources and named on the tool's own pages. Where a number is a rounded or typical value rather than a measurement, the page says so. The text on each page is written for the tool it sits in; the same paragraphs are not reused across tools, and this index does not copy tool text.
Something wrong?
A wrong result matters more than a broken layout. The useful report names the tool, the exact input, the answer it showed and the answer you expected. Corrections are checked against the cited source and, where the tool was wrong, fixed on the page. Reports about wording, unclear explanations or missing sources are welcome too, since they help the next reader as much as a corrected number does. The address to send a report to is on the about page, together with a description of who runs the site.