How our calculations work

The calculations run in your browser

For the calculators, the converters and the text and file tools — the overwhelming majority of the catalogue — no server does the arithmetic and no database holds your inputs. This has a consequence worth stating: the same inputs always produce the same result, and the code producing it is on your machine, so nothing about the answer depends on a service being up, on your account, or on the day.

Three things on this site do talk to a server, and it would be dishonest to leave them out. A few tools have no choice: a DNS lookup queries a resolver, and a temporary number receives a real SMS — both are flagged on their own pages. The dictionary is served from our database rather than shipped to your browser. And we count page views and searches with our own code, described in full on the cookies page. Everything else — every calculator, every converter, every file and image tool — never sends what you typed anywhere.

Where the reference data comes from

Most tools are pure arithmetic and need no data at all. The ones that do use published references, named on the tool's own page:

• Growth and health percentiles — the WHO and CDC reference tables, used as published (the LMS parameters, not a curve redrawn by eye).
• Marketplace and payment fees — each platform's own published schedule, per country, each carrying the date it was last read against the source.
• Astronomical dates — seasons, moon phases, sunrise, zodiac boundaries — from standard astronomical algorithms, including the ΔT correction that separates civil time from the sky.
• Tax, VAT and salary figures — the official national scales, with the tax year stated on the page. A fiscal calculation without a year is not a calculation.
• Unit conversions — the SI definitions and the internationally agreed conversion factors, not rounded intermediates.

Rounding, and why it happens last

Calculations run at full precision and are rounded only for display. A figure shown to two decimals was not rounded before being fed into the next step — that is the difference between a loan schedule that closes to the cent and one that drifts by a few euros over twenty years.

Data ages, and the page says when it was checked

A fee schedule or a tax scale is true on a date and can quietly stop being true afterwards. Tools built on such data carry the date they were last read against their source. If you are reading well after that date, treat the result as an estimate and check it against the official schedule.

What these tools are not

They are not medical, legal, tax or financial advice. A health calculator gives you an indication against a population reference; it does not know your history and cannot diagnose. A tax calculator estimates for one stated year and one stated jurisdiction; it does not know your situation. Where a decision matters, the number here is a starting point for a conversation with someone qualified, not a substitute for it.