Blog
Guides, formulas, and tips behind the tools.
How to Calculate a Discount (And Check a Store Isn't Overcharging You)
The formula behind percentage-off discounts, how to calculate stacked discounts correctly, and a quick way to sanity-check any sale price.
How to Calculate Your Exact Age in Years, Months, and Days
Why "this year minus birth year" gets your age wrong for part of the year, and the correct way to calculate exact age.
How to Calculate Percentage Increase (With Examples)
The exact formula for percentage increase and decrease, worked examples for raises and price changes, and common mistakes to avoid.
How Reading Time Estimates Actually Work (Words Per Minute Explained)
The words-per-minute figures behind "X min read" labels, where they come from, and how to estimate reading time for your own writing.