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finance
Car Loan Affordability Calculator vs the 20/4/10 Rule: Which One Is Lying to You?
A payment calculator says the average $44,156 car loan is affordable on a median income. The 20/4/10 rule says you need $146,000. Here is the math.
8 min read
finance
Investment Growth Calculator: How Compound Interest With Monthly Contributions Adds Up
How an investment growth calculator models monthly contributions, time, fees, and taxes — with the real annuity formula and checked math.
8 min read
finance
Markup vs Margin Calculator: The Formulas, the Table, and the Pricing Error That Costs You Money
Markup vs margin calculator guide: the two formulas, a 10-300% conversion table, and the exact pricing error that underprices every SKU.
8 min read
finance
Compound Interest Calculator vs a Savings Account: What Actually Grows Your Money
The formula, the APY that matters, and why a 0.38% bank account vs a 5% HYSA is a $462/year gap on $10k. Run the math before you pick.
9 min read
finance
Best Mortgage Calculators in 2026: Free, Paid, and the Five Inputs That Actually Matter
Most online mortgage calculators give you the wrong number because they leave out taxes, insurance, and PMI.
9 min read