Percentage Calculator

How to use

1. Find the sentence that matches your question, such as 30 is what percent of 200?
2. Replace the numbers in its blanks. The answer sits where the question mark would be and redraws on every keystroke; the sentence you last touched also becomes the figure at the top.
3. Copy the address bar if the calculation is worth keeping or sending. Your figures travel inside the link.

About this tool

Five questions, one page, each written as the sentence you would type into a search box with its blanks inline. Between them they cover the percentage questions that actually come up: what X% of a number is, what percent one number is of another, how much a figure moved between two readings, what a price becomes with a percentage taken off or added on, and what the whole was when you only know a part. Every question answers itself while you type, and the one you are working on is the large figure at the top.

The numbers waiting when you arrive are worked examples in their own right. 15% of 200 gives 30. 30 out of 200 gives 15%. 100 to 125 reads 25% increase, 80 at 25% off reads 60.00 (you save 20.00), and 60 being 75% of something works back to 80. Type over whichever pair matches your question and leave the rest sitting there.

The change question is the one people misread most. The size of the move is the difference divided by the absolute starting value, and the word comes from whether the reading went up or down, so a balance climbing from −100 to 100 reads a 200% increase rather than a decrease. A second line gives the plain difference in the same units. A start value of zero has no answer at all, and the From box says The starting value can't be zero.

Everything you type lands in the page address as you go, under short names like from and to, so a copied link reopens with the same figures and the same results. Answers are rounded at four decimal places, which is more precision than a shopping trip or a tax line will ever want. It does mean 1 out of 3 comes back as 33.3333%.

Where it stops

• The change question reports relative change first. A move from 10% to 12% shows as a 20% increase, and the line under it gives the 2-point difference in the same units.
• An empty field is never read as zero. Clear the Number box and the first answer keeps its last value, dimmed, while the field says what it is waiting for; a Whole of 0 is refused at the field with The total can't be zero.
• Only the price question is treated as money: it works in whole cents and prints two decimals, so 19.99 at 15% off is 16.99 and the 3.00 saved adds back to the price exactly. No currency symbol is shown, and other answers keep up to four decimal places.
• A discount is bounded at 100%, since nothing can lose more than its whole price. To add tax or a markup, switch the price question to on top, which takes any percentage from 0.