Math & Everyday
How to Calculate a Tip (and Split the Bill)
A fast mental method for 15%, 18%, and 20% tips — plus how to split the total across the table.
Guides
Calculator guides & articles
The reasoning behind the numbers — how to estimate a project, plan your taxes, read your health metrics, and make everyday math easy.
Math & Everyday
How to Calculate Exact Age in Years, Months, and Days
Counting age precisely means handling different month lengths and leap years. Here's the method behind it.
Math & Everyday
How to Calculate Percentages (3 Common Cases)
Find a percentage of a number, figure out what percent one number is of another, or calculate percent change.