Guides & explainers
In-depth, plain-spoken guides to the maths and money behind everyday decisions. Each one is written to be useful on its own — not just to feed a calculator.
Finance
How loan amortization actually works
Why the first years of a loan feel like you are barely denting the balance, and how extra payments rewrite the whole schedule.
Read guideUnderstanding US sales tax
State rate versus the rate on your receipt, why two nearby shops charge different amounts, and how online orders get taxed.
Read guideSimple vs compound interest
How the two are calculated, why compounding frequency is a real cost, and when the difference actually bites.
Read guideBusiness
Math
Percentage change vs percentage points
The distinction behind countless misleading headlines, with the formulas for both and worked examples.
Read guideThe Pythagorean theorem, explained
The geometry behind the formula, the triples worth memorising, and how builders use it to square a corner.
Read guideRatios and proportions, explained
What a ratio actually compares, how to scale one without wrecking it, and the mistakes that cause drift.
Read guideLogarithms, explained simply
A logarithm is just a backward exponent. Here is how to read one, and why decibels and data sizes use them.
Read guideHealth & Fitness
TDEE, BMR and macros, explained
How the three numbers relate, the order to use them in, and how to adjust when the scale stops moving.
Read guideUnderstanding body composition
Three numbers that describe different things, why one alone misleads, and how to track progress the scale hides.
Read guideHome & Construction
How to budget a roof replacement
The factors that move a roofing quote, how to compare bids fairly, and where homeowners overspend.
Read guideHow to estimate materials for a home project
The step from measurements to an order you can actually place, including waste, coverage, and rounding.
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