Calculator Den Guides
Plain-English explainers on the maths behind our calculators. Each one walks through the idea with real examples, then points you to the tool that does it for you.
- Markup vs Margin: What's the Difference? A plain-English guide to markup versus margin, with a worked example and the conversion formulas.
- Compound Interest Explained (With Examples) A beginner-friendly explanation of compound interest, the formula, a worked example, and why time is the biggest factor.
- How to Calculate Percentages A clear guide to the three everyday percentage calculations, with examples, common mistakes, and quick mental shortcuts.
- How Interest Rates Work A plain-English guide to how interest works across savings, loans, credit cards and mortgages, plus APR vs APY.
- VAT Explained A simple guide to how VAT works, inclusive vs exclusive prices, and how to add or remove it correctly at any rate.
- Simple vs Compound Interest The difference between simple and compound interest, with a side-by-side example and where each one is used.
- BMI Explained A clear guide to body mass index: the formula, the categories, and why BMI is only a starting point, not a diagnosis.
- APR vs APY: What's the Difference? What APR and APY mean, why they differ, and which to compare for loans versus savings.
- Gross vs Net: What's the Difference? The difference between gross and net for pay, income and profit, with clear examples.
- How to Calculate Your GPA A step-by-step guide to calculating GPA on the 4.0 scale, with a worked example and weighted-GPA notes.
- How Much House Can I Afford? How to work out a realistic home budget using the 28/36 rule, your income, debts, down payment and rate.
- Mean, Median and Mode Explained Definitions, formulas and a worked example for the three averages, plus when to use each.
- Debt-to-Income Ratio Explained What DTI is, how to calculate it, what counts as healthy, and how to lower it before you borrow.