Percentage Math Blog
Short, practical guides with real numbers. Each one links to a calculator so you can check your own figures.
How to Find Percent Off: 3 Fast Methods (With Examples)
Three quick ways to work out a percent-off discount in your head, on a phone, or in a spreadsheet, plus the stacking-coupon trap.
Markup vs Margin: Formulas and Conversion Chart
Markup divides profit by cost; margin divides it by price. See why a 50% markup is only a 33% margin and how to convert between them.
How to Calculate the Percentage of a Number
The two everyday percentage questions, solved with one rule: X% of Y, and X out of Y as a percent. Includes test-score examples.