Guides

Plain-language explainers for the math behind the calculators — each one links to the tools that put it into practice.

How discounts, markups, and tax actually work.

What's the real difference, and why it compounds.

Two different numbers, two different questions.

Explained with real numbers, not just theory.

Why kg, lbs, and miles still coexist.

How weighted and unweighted GPA actually work.

Why "5 business days" is trickier than it sounds.