Utilario is a collection of small online tools that answer one question each and then get out of the way. No account, no installation, no dashboard — open the page, get the number, close the tab.
Who makes it
Utilario is built and maintained by David Rodriguez Rodriguez, working from Las Palmas de Gran Canaria, Spain. It is an independent project rather than a company, which means there is one person deciding what gets built, one person responsible when a calculation is wrong, and no marketing department between you and the tools.
You can reach me directly at daorchaia@gmail.com. Messages about incorrect results go to the top of the list.
Why it exists
Most everyday calculations do not deserve an app. You need to know what 20% off means in actual money, how many working days are left before a deadline, or whether a photo will fit inside an upload limit. The existing options tend to be one of three things: a page buried under an essay you have to scroll past, a site that wants your email first, or a tool that uploads your data to a server it has no reason to touch.
Utilario is the reaction to that. The tool sits at the top of every page. The explanation sits underneath, for the people who want it. Nothing asks you to sign up, and where a calculation can happen on your own device, it does.
How the tools are checked
Every tool is verified two ways before it is published, and both checks run again on every change:
- The calculations are tested against known answers. Each tool has assertions covering its normal cases and its awkward ones — leap days, shifts that cross midnight, zero interest rates, ranges entered backwards, breaks longer than the shift. A tool that produces a wrong answer fails the build and does not ship.
- The page itself is audited. An automated gate checks that every page has genuine explanatory content rather than filler, that no two pages are near-copies of one another, and that links, metadata and structured data are valid. Pages that fall below that standard are rejected before publication.
This is not a claim that the site is flawless — it is a claim about what happens when something is wrong. Two real bugs have been caught and fixed this way since launch: a percentage result that dropped a trailing digit, and an image tool that quietly stopped updating during fast edits. If you find a third, tell me and it gets fixed rather than argued about.
That said, please read the Terms of Use: these are general-purpose tools, not professional advice. Tax rates, holiday calendars and employment rules vary by country and change over time. For anything with financial, legal or medical consequences, verify the result independently.
Your data
Every tool currently on Utilario runs in your browser. The text you paste, the dates you enter and the images you open are processed on your device and never uploaded. There are no accounts, no analytics and no visitor tracking. If a future tool ever needs to send data to a server, that will be stated plainly on the tool's own page before you use it. The Privacy Policy has the full detail.
How it is funded
Utilario is free and is paid for by advertising. Advertisements are marked, kept out of the way of the tool itself, and never used as a condition of getting an answer. Advertising has no influence on what the calculators return — there are no sponsored results and no affiliate links inside the tools.
What comes next
New tools are added regularly, chosen by what people ask for rather than by what ranks well. If a task you do often is missing, describe the problem in your own words — that is how most of the tools here started.