APR vs. APY: Nominal and Effective Rates Explained
What APR and APY each measure, why compounding makes them differ, how federal rules define them, and how to use each one to compare loans and savings accounts fairly.
FinanceGuides
Plain-English guides that explain the maths behind our calculators: percentages, interest, loan amortization and more.
Fractions, Decimals and Percentages: How to Convert Between Them
How to turn any fraction into a decimal or percentage and back again, which fractions give repeating decimals, and a conversion table for the values you meet most often.
MathHow Leap Years Work
Why the calendar needs leap years, the Gregorian rule for which years have a February 29, and how leap days affect date calculations, ages and birthdays.
Time & DateHow Loan Amortization Works: Why Early Payments Are Mostly Interest
A plain-English explanation of loan amortization — how a fixed payment is split between interest and principal, why the balance falls slowly at first, and what changes the total cost.
FinanceHow Much House Can I Afford? Payments, Ratios and Down Payments
How lenders weigh income and debt, what goes into a full monthly mortgage payment, and how the rate, down payment and PMI change the price range a budget supports.
FinanceHow to Calculate Hours Worked
A step-by-step method for timesheets, from clock times to decimal hours, including overnight shifts, unpaid breaks, rounding practices and weekly totals.
Time & DateHow to Calculate Percentage Change
The percentage change formula, how it differs from percentage difference and percentage points, how to handle negative starting values, and why successive changes don't simply add up.
MathMean, Median and Mode: Which Average Should You Use?
What the mean, median and mode each measure, how outliers and skewed data pull them apart, and how to pick the average that describes your numbers honestly.
MathSimple vs. Compound Interest: How They Differ and Why It Matters
How simple and compound interest are calculated, how far apart they grow over time, and how to tell which one applies to a loan or savings account.
Finance