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Guides
The math behind a good deal
Short, specific guides on the arithmetic that decides whether a purchase is actually cheaper. Every guide carries a worked example and a decision rule you can use in the aisle.
Unit pricing
5 guidesHow to calculate unit price correctly
The shelf tag is often wrong or inconsistent — here's the arithmetic that actually holds up.
6 min read · updated 2026-01-12
How to compare package sizes without getting fooled
Manufacturers change package sizes far more often than they change prices — here's how to catch it.
6 min read · updated 2026-01-10
Sale price is not best value
A 30%-off sticker on the wrong package size can cost more per unit than the full-price alternative next to it.
6 min read · updated 2026-01-20
How to compare grocery prices fairly across stores
Comparing a receipt total across two stores tells you almost nothing unless the basket, sizes, and quality tier match.
7 min read · updated 2026-01-24
Why a cheaper package can cost more per unit
The smallest sticker price on the shelf is frequently the worst deal — packaging economics work against small sizes.
6 min read · updated 2026-01-26