Money guides that show their work
Calculators give you a number; guides make sure you understand it. Every guide below explains one money concept in plain English, works a complete example with real figures, and links to the calculator that runs the same math on your own numbers.
Saving & Growth
How Compound Interest Works
Interest on interest, the formula behind it, and why $5,000 plus $150 a month can become $112,987.
How Much Should You Save Each Month?
Work backwards from a goal: the exact monthly deposit for $20,000 in 3 years, plus the percentage rules.
How to Build an Emergency Fund
Three to six months of essentials — how to size it, where to keep it, and how long it really takes.
What Is CAGR?
The compound annual growth rate explained: why 60% over 5 years is 9.86% a year, not 12%.
Loans & Mortgages
How to Pay Off a Loan Faster
The strategies that save real interest — an extra $100 a month ends a loan 13 months early.
15-Year vs 30-Year Mortgage
One $350,000 loan, both terms: a $247,608 interest difference and the middle path between them.
How Amortization Works
Why your first mortgage payment is $1,250 interest and only $248.88 principal — and why that flips.
How Extra Payments Save Interest
Interest follows the balance — so $200 extra a month on a mortgage saves $109,927.51.
Everyday Money
APR vs APY
One is the true cost of borrowing, the other the true yield on saving. An 8% loan can be a 10.08% APR.
How to Convert Salary to Hourly Pay
The 2,080-hour method: $62,400 a year is $30.00 an hour — plus overtime, leave, and freelance adjustments.
Guides and calculators, together
Each guide is written to be read alongside its calculator. The guide explains the concept and proves the method on a fixed example; the calculator then runs the identical math on your figures, instantly. If a number in a guide ever looks different from what the calculator shows, the inputs differ — every worked example states its inputs in full so you can reproduce it exactly.
Start wherever your current question lives: growth questions in the compound interest and CAGR guides, borrowing questions in the amortization and extra payments guides, and everyday conversions in the salary and APR vs APY guides.