Overview
Percent means “per hundred.” Most everyday problems reduce to finding a percent of a number, expressing a ratio as a percent, or measuring change between two values.
Percent of a number
Multiply by P/100. This is the form used for discounts, tips, and tax estimates.
Percent of total
Divide the part by the whole, then multiply by 100.
Percent change
Always divide by the original value, not the new one.
Try the calculator
Use the free Percentage Calculator for live numbers, then come back to this guide anytime you need a quick refresher.