About This Site
Four Function Calculator is a small, independent set of free math tools. Every calculator here shows its working, runs entirely in your browser, and is built to load fast on a slow connection.
What this site is
This site started as one thing: a plain four-function calculator that loads instantly and does not ask you for anything. It has grown into a set of arithmetic, percentage, fraction and statistics calculators built on the same principle.
The principle is that an answer without the working is only half useful. If you are checking a discount, a grade or a lab result, you usually need to know how the number was reached — either because you have to show it to someone, or because you want to be sure the calculator understood the question the way you meant it. So every tool here prints the formula with your own numbers substituted in, and expands to show each step.
How the calculators are built and checked
Each calculator is plain JavaScript running on your device. There is no server round-trip, no framework and no third-party script, which is why the pages load quickly and keep working if your connection drops.
Every engine is covered by an automated test suite that checks it against known answers — including the awkward cases: even and odd medians, stacked discounts, banker’s rounding, negative remainders, right-associative exponents and arbitrary-precision integer math. Worked examples in the written content are checked against the same engines, so the numbers on the page and the numbers in the calculator cannot drift apart.
If you find an answer you think is wrong, please say so — a reproducible example is the most useful thing you can send.
The rules this site follows
- No accounts and no sign-up walls. Every tool is fully usable the moment the page loads.
- Nothing you type is transmitted. Calculations happen in your browser and stay there.
- No display advertising. The pages carry no ad units, pop-ups or interstitials.
- No invented authority. There are no fake author bylines, fake credentials or invented statistics anywhere on this site.
- Corrections are made, not buried. If something here is wrong, it gets fixed.
Who runs it
The site is published by DigiKasvu, a registered sole proprietorship in Finland (Business ID 3612228-8). It is a small independent project rather than a company product.
You can reach the site at the contact page.
A note on accuracy
These calculators are provided for general use. They are tested carefully, but they are not a substitute for professional advice in financial, medical, engineering or legal contexts, and you should verify any figure that matters before relying on it. See the terms of use for the full position.