Guides

Short explainers on the ideas behind our calculators.

• Percentages Explained: Parts, Changes, and Common TrapsHow percentages work, how to calculate percent change correctly, why discounts don't add up, and the difference between percent and percentage points.
• How Interest Works: Simple, Compound, and Loan PaymentsA plain-English guide to simple and compound interest, compounding frequency, and how loan payments are split between interest and principal.