Articles & guides
Learn the math behind the calculators — practical guides on money, health, numbers and measurement, written in plain language.
Unit Conversions Made Simple: A Guide to Converting Anything
From meters to miles to megabytes: learn the one strategy that makes any unit conversion easy, plus the traps that catch everyone.
Percentage Calculations: A Practical Guide with Real Examples
Master the three core percentage problems — percent of a number, percent change, and part-to-whole — with formulas and everyday examples.
Retirement Planning Basics: How Much You Need and How to Get There
A step-by-step retirement planning framework: estimate your goal, harness compound growth, and build a savings plan you'll actually stick to.
The Compound Interest Guide: How Wealth Compounds (and How to Use It)
Compound interest is the eighth wonder of the world — here's the math, the magic of time, and practical strategies for savers and investors.
BMI Explained: What It Measures, Its Limits, and How to Use It
A practical guide to Body Mass Index — how the math works, what the categories mean, and where BMI falls short.
How Mortgage Interest Works: Amortization, Rates and Real Costs
Understand exactly how mortgage interest is calculated, why early payments are mostly interest, and how rates and terms shape what you pay.