Guides and explainers for math, finance, and unit conversion — linked to the calculators and formulas you can use right away.
29 articles
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Finance guides·12 min read
A fixed-rate loan payment blends interest on the remaining balance with principal repayment — early payments are mostly interest.
Finance guides·11 min read
Compound interest means you earn interest on both the original principal and on interest already added — growth accelerates over time.
Finance guides·10 min read
A practical guide to sale prices and sales tax: find the discount, the pre-tax total, and the final bill without mixing up the steps.
A fixed-rate mortgage payment blends interest on the remaining balance with principal repayment — and your full housing payment often includes taxes and insurance too.
An amortization schedule lists every payment’s interest, principal, and remaining balance so you can see how a loan pays down over time.
ROI compares net gain to cost as a percent — a simple scorecard for projects, ads, and investments when you define the inputs clearly.
Turn a target balance into a monthly savings plan — with or without compound interest — so your timeline and deposit size stay realistic.
APR is a nominal annual rate used widely for loans; APY (or EAR) includes compounding so you can compare true yearly growth or cost.
Simple interest grows in a straight line on the original principal; compound interest grows on principal plus accumulated interest. Knowing which one applies changes what you pay or earn.