Math calculators
Percentages, shares and changes — the everyday arithmetic behind discounts, markups and comparing numbers.
1 tool in this section
How to choose a tool
Percentages come up when you compare discounts, markups or price growth. This tool shows which base the percentage is calculated from — the most common source of mistakes.
Every calculation runs in your browser: the page never sends the numbers you type to a server and keeps no history. If a result raises questions, each tool page ends with short answers about allowances and limitations.