Percentage Calculator

Shopping, grades, and markups all ask a percent question, but not the same one. Percentage Calculator has three modes so the formula matches the question.

Three modes, two numbers

“What is X% of Y?” multiplies Y by X divided by 100. Ten percent of 80 is 8. “X is what % of Y?” divides X by Y and multiplies by 100. Twenty out of 80 is 25 percent. The whole cannot be zero. “% change from X to Y” subtracts the start from the end, divides by the absolute value of the start, and multiplies by 100. A move from 80 to 100 is 25 percent. The start cannot be zero. A drop from 100 to 80 is negative. Labels on the two fields change with the mode, so read them before you type.

Where people mix the modes up

A discount is not the change mode unless you type the old price and the new price. Discount Calculator takes an original price and a discount percent and returns savings and a final price in one step. VAT Calculator adds or extracts a tax rate. Tip Calculator splits a bill. Those pages exist so you do not have to reshape a percent-of problem into a tax or a tip. Percent change uses the absolute value of the starting number, so a change that starts negative is measured against the size of that start, not against a signed denominator that would flip the meaning.

What this tool will not do

It will not stack two discounts, add sales tax after a markdown, or convert a fraction to a percent in a separate fraction field. It shows one result line for the mode you picked. There is no history of earlier calculations. The math runs in this browser tab. Age Calculator, Countdown Timer, and Week Number are date tools, not percent tools. If you need X percent of Y and also the price after tax, run this page for the percent, then VAT Calculator on the result.