Percentage calculator that shows the working.

A percentage calculator turns an awkward piece of arithmetic into a single answer. You know two numbers, you need the third, and you need it before the conversation moves on — the tip on a restaurant bill, the real saving on a sale sticker, the pay rise you have just been offered, the mark you actually scored. This is a free online percentage calculator built for exactly that moment: type two numbers, press Calculate, and read the answer with the working underneath it.

The reason for showing the working is simple. An answer you cannot check is an answer you have to trust blindly, and percentages are the one piece of everyday maths people most often get subtly wrong. Every result here comes with the formula, your own numbers substituted into it, and each step written in plain language — so you can confirm the calculator did what you meant, and repeat it yourself next time.

The three questions behind almost every percentage

Percentage problems look endlessly varied, but nearly all of them involve the same three quantities: a part, a whole, and the percentage connecting them. You always know two. Identifying which one is missing tells you which calculation you need, and that identification — not the arithmetic — is where most mistakes happen.

• What is X% of Y? You have the percentage and the whole, and want the part. This is tips, commission, tax amounts and shares of a budget.
• X is what percent of Y? You have the part and the whole, and want the percentage. This turns 38 out of 50 into 76% —calculate it here.
• X is Y% of what number? You have the part and the percentage, and want the whole. This is how you recover an original price from a deposit or a post-discount total.

All three live on the main percentage calculator, switchable with a single tap, so you do not have to work out which page you need before you can start.

Measuring change: increase, decrease, difference

The second family of calculations compares two numbers rather than relating a part to a whole. These are the ones that get muddled most often, because three different formulas all sound like they are answering the same question.

An increase percentage calculator measures growth against where you started: 100 to 150 is a 50% increase. A percentage decrease does the same in the other direction. The percentage change calculator handles either, and states which one happened rather than leaving you to interpret a minus sign.

Percentage difference is the one that is genuinely different. It compares two values against their average, so neither is treated as the baseline and swapping them gives the same answer. Use change when one value came before the other; use difference when they are simply two readings. On the values 100 and 120, change says 20% and difference says 18.18% — both correct, answering different questions.

Percentage calculators for specific jobs

Most percentage questions arrive wearing the vocabulary of a particular task, so each one has its own page with the right field labels, the right secondary figures and the conventions that apply to it:

• The grade percentage calculator converts marks into a percentage and a letter grade. It doubles as a test percentage calculator — the arithmetic is identical whether the paper was a quiz or a final.
• The average percentage calculator averages a list of percentages, and weights them by group size. Averaging percentages from differently-sized groups without weighting is one of the most common statistical errors there is, so it shows both answers.
• The win percentage calculator turns a win–loss record into a win rate, counting ties as half a win the way league tables do.
• The tax percentage calculator adds tax, strips it back out of a total, or works out the rate you were charged — for sales tax, VAT or GST at any rate you enter.
• The discount calculator shows the money off and the price you actually pay, and explains why stacked discounts never add up the way the sign implies.

Health and fitness percentages

Two more tools cover the percentages people track about themselves. The weight loss percentage calculator works out what share of a starting weight has gone, which is the fair way to compare progress between people who started at different weights — and the reason challenges are scored this way rather than in raw pounds. The body fat percentage calculator estimates body fat from tape measurements using the US Navy method, in centimetres or inches.

Both are arithmetic tools, not clinical ones. They are useful for tracking a direction of travel over weeks and months; they are not a substitute for advice from a doctor or a body-composition scan, and neither page pretends otherwise.

Built to be quick, honest and private

Speed matters more than features on a tool like this. You arrive from a search, you need one number, and you should be gone within seconds. Every page is static, the calculator loads with the page rather than after it, and the whole thing weighs a few kilobytes of JavaScript — so it works on a slow phone connection as well as it does on a laptop.

Everything here runs as a percentage calculator online — nothing to install, no account to create, and no waiting on a server. It is also honest about precision: when a result is a repeating decimal it is marked with ≈ rather than presented as exact, and the calculation behind it always ends at the figure shown. Invalid input produces a plain-English explanation rather than NaN, and the cases that genuinely have no answer — a percentage of zero, a change from zero — say so instead of returning something misleading.

Nothing you type is sent anywhere. Every calculation runs in your own browser, there is no account, the site sets no cookies, and even the fonts are served from this domain rather than a third party. Your recent calculations are saved in your browser alone, and the Clear button removes them.

If you want the reasoning rather than the answer, the guide to calculating percentages covers the method and the mental shortcuts, and the formula reference sets out every formula side by side with the distinctions between them made explicit.