What do you want to work out?

A free online calculator for the sums that actually come up

Most people do not need a scientific calculator. They need to work out a tip, check whether a sale is really a saving, split a bill without an argument, or turn a set of marks into a percentage. This is an online calculator built for exactly those moments, and nothing else.

Every calculator here is free, works in the browser with no sign-up, and asks its questions in ordinary words. There is no equals button to hunt for — the answer appears as you type, and underneath it we write out in a plain sentence how we got there, so you can check it makes sense rather than taking our word for it.

What you can work out here

The simple calculator handles everyday sums — adding, taking away, multiplying and dividing — with big buttons and full keyboard support on a computer.

For money, the percentage calculatortells you what a percentage of an amount comes to, which is the sum behind a deposit, a commission or a saving. The tip calculatortakes a bill and shows both the tip and the total to pay, with one tap for the common amounts. The discount calculator takes the number off a sale sign and shows what you actually pay at the till. And thebill split calculator divides any total between any number of people, tip included — it works just as well as a rent split calculator for housemates, or for a taxi, a group present or a shared shop.

For school and college, themarks to percentage calculatorturns a score like 450 out of 600 into 75%, and understands a score written as a fraction if that is how you have it. Thefinal exam calculator works out what grade you need on your last exam to pass a class, and says so plainly when the grade you want is no longer reachable. Thefinal grade calculator shows how to calculate a final grade when coursework and exams count for different amounts — which is where most people go wrong, because averaging the scores quietly gives the wrong answer.

There is also apercentage change calculatorfor comparing an old amount with a new one, which is what you want for a pay rise, a rent increase or a price that has crept up.

Built for people who find maths stressful

Most calculator sites are built for people who already know which calculation they need. They greet you with a wall of two hundred tools and fields labelled things like "base value" and "rate of change". If you were confident about the maths, you would not be looking it up.

So the calculators here are named after the question in your head rather than the technique. Not "percentage increase" but "how much did it go up or down". Not "weighted mean" but "what is my final grade". Every field asks a question in words, every answer is explained in a sentence, and the examples in the boxes are marked as examples so nobody mistakes them for numbers they have to keep.

What makes the best online calculator?

Search for the best free online calculator and you will find plenty that are technically impressive and genuinely hard to use. The ones worth keeping open have a few things in common, and none of them are features.

It should load immediately, because you are usually standing somewhere with one hand free. It should ask its questions in words you already use, not in labels borrowed from a textbook. It should show its working, so you can tell whether the answer is sensible rather than trusting it blindly. It should not ask who you are. And it should be honest about what it cannot do — this simple calculator divides, for example, but it cannot yet show an answer back as a fraction, and saying so is more useful than pretending otherwise.

That is the standard we are building to. Whether we have reached it is for you to judge, and if something here is confusing then the fault is ours rather than yours.

Free, private, and quick

Nothing you type is sent anywhere. The sums happen in your browser, and the numbers disappear when you close the page — we never see them and never store them. There is no account and no email address to give. We do count visits, so we know which calculators are worth improving; what that involves is set out in plain words on theprivacy policy page.

Two settings are remembered so you do not have to set them twice: whether you chose light or dark, and which grading scale you picked. Both are kept in your own browser and say nothing about who you are. Your marks, your salary and your bill are never among them.

The pages are built to load quickly on a cheap phone with a poor connection, because that is where people usually are when they need to check a bill. If something here still does not make sense, that is our fault rather than yours — thecommon questions page explains percentages, tips and grades from the beginning, without assuming anything.