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Plain-English articles on the math behind the calculators — what the formulas assume, where the rules of thumb come from, and when to break them.

A note on how these are written: personal finance and health advice online tends to come in two flavors — vague encouragement, or rules of thumb stated as laws of physics. These articles try for a third thing. Every piece works through actual numbers, names the research or formula it leans on, and spends real space on the situations where the standard advice fails, because those edge cases are usually where readers actually live. Each article pairs with one of the calculators, so you can run your own numbers against whatever the article claims.

Debt

Mortgages & housing

Solar

Saving & budgeting

Health