Free Online Percentage Calculators: Math, Change & Discounts
Calculateos helps you solve everyday percentage problems instantly, without complex formulas or spreadsheets.
What is X% of Y?
X is what percent of Y?
X is Y% of what?
Increase or decrease between two numbers
Find the percentage increase or decrease between two values.
Choose the Right Percentage Tool for Your Task
Use four dedicated calculators to solve percent of, what percent, percent of what, and percentage change with step-ready formulas.
Every result is optimized for quick checks on mobile and desktop so you can move from question to answer in seconds.
Each calculator on this page focuses on one specific problem so you always get the right answer:
- Percent of a Number Calculator: Find the exact part of a whole (answers questions like: "What is 15% of 80?").
- What Percent Calculator: Compare a part to a whole (answers questions like: "45 is what percent of 180?").
- Percent of What Calculator: Reverse the math to find the original number when you already know the part and the rate.
- Percentage Change Calculator: Measure the exact percentage increase or decrease between a starting and ending value. Perfect for tracking month-over-month business metrics, price changes, and exam score improvements.
Fast, Mobile-Friendly, and Easy to Use
We designed Calculateos with mobile visitors in mind. Enjoy large input fields, clear labels, and easily readable results on your phone, tablet, or desktop.
Want to understand the math behind the answers? Review our formula cards below or open our quick percentage calculation guide in the site navigation.