Blog
Short guides to the maths and formats behind the tools, with worked examples.
Percentage change vs percentage points
Why a rate moving from 4% to 5% is a 25% increase, and when to say “one point”.
Margin and markup are not the same number
Two ways to describe profit on a sale, with worked examples for pricing.
Five common JSON errors and how to read them
Trailing commas, single quotes and other mistakes, with the messages browsers show.