About
Utileno is an independent utility project: a collection of small, fast online tools — calculators, converters and text utilities — that run directly in your browser.
There is nothing to install and no account to create. Open a tool, type your input, and you get the answer immediately.
It exists because the everyday version of these tools is usually worse than it needs to be: a single answer buried under interstitials, or a page that uploads what you typed to get a result that arithmetic could have produced on your own device.
Privacy first
The tools on this site process your input locally in your browser. What you type into a calculator or paste into a text tool is not sent to our servers — there is no upload step and no account to create. See the Privacy page for what is stored on your device and how analytics and advertising work.
Why these tools
We build tools around real, everyday questions: what is a percentage of a number, how many days until a date, how many words are in a text. Each tool focuses on answering one question well instead of hiding many features behind menus.
How we decide what to build
A tool gets built when there is a specific question people actually ask and a definite, checkable answer: how many days until a date, what a lunar birthday falls on this year, how many square metres a Korean property listing means.
If a question has no single correct answer, or answering it responsibly needs professional advice, we leave it alone. The tools here compute; they do not advise.
How the tools are built
Each tool is a small, self-contained calculation, unit-tested against known-correct results before it ships. Date arithmetic is tested against leap years and month-end edge cases; the Korean lunar calendar converter is checked day by day across its whole supported range against a reference implementation of the Korea Astronomy and Space Science Institute (KASI) calendar data.
The site is static: pages are pre-rendered and the calculations run as plain JavaScript in your browser. That is why results appear instantly, work on a slow connection, and keep working even if our servers are unreachable.
Where the data comes from, and where it stops
Where an authority publishes the underlying data, the tool follows it and the page names the source: the Korean lunar calendar follows the Korea Astronomy and Space Science Institute (KASI) dataset, and the public-holiday calendar follows the substitute-holiday rules currently in force.
Every tool has a boundary, and we would rather state it than paper over it. Each page names its supported range and the cases it does not handle — the romanizer lists the sound changes it cannot resolve without a dictionary, the lunar converter names its year range, the date calculator says where its month figure is an approximation. If a result depends on something we cannot verify, the page says so instead of guessing.
English and Korean
Every page exists in both English and Korean, and the copy for each language is maintained separately rather than generated from the other, so examples and explanations fit their own context.
Some tools exist because they answer questions specific to Korea: converting pyeong to square metres when reading a property listing, finding this year’s date of a lunar birthday, or checking which substitute public holidays fall in a given year.
Feedback
Missing a tool you need, or found a bug? Feedback is read and it shapes what gets built next — see the Contact page.