Overview
Introduction
"What is 15% of 200?" is one of the most common quick calculations there is, whether you're figuring out a tip, a tax, or a share of a total.
This calculator gives you the answer instantly as you type, with no need to reach for a spreadsheet or do the division by hand.
What Is Percentage Calculator?
A calculator that finds what a given percentage of a number equals, by converting the percentage to a decimal and multiplying it by the base number.
It runs entirely in the browser as part of this site's Math Tools collection. Nothing you type is sent to a server.
How Percentage Calculator Works
The percentage is divided by 100 to convert it to a decimal fraction, then multiplied by the base number to get the result.
The calculation runs synchronously in JavaScript on every keystroke, recomputing the result from the current input values.
When To Use Percentage Calculator
Use it whenever you need to find a portion of a number expressed as a percentage, a discount amount, a commission, a share of a budget, or a grade on a test.
It's a fast way to get the answer without opening a calculator app or doing the arithmetic by hand.
Often used alongside Percentage Of Calculator, Reverse Percentage Calculator and Percentage Change Calculator.
Features
Advantages
- Results update instantly as you type, no submit button required.
- Handles negative numbers and percentages over 100% correctly, not just the common 0-100% case.
- Simple, single-purpose interface: enter a percentage and a number, get the answer.
Limitations
- Only answers the direct 'X% of Y' question; use Percentage Of Calculator, Percentage Change Calculator, or the other related tools for the reverse or comparative questions.
- Uses standard JavaScript floating-point arithmetic. That's precise enough for everyday use, not for high-precision financial or scientific work.
Examples
Best Practices & Notes
Best Practices
- Double-check which number is the percentage and which is the base, swapping them gives a different (usually very different) answer.
- For financial calculations involving money, round the final result to two decimal places yourself according to your currency's convention.
Developer Notes
Implemented as `(percent / 100) * base` on plain JavaScript numbers; the display value is rounded to 6 decimal places and trailing zeros are trimmed so whole-number results like `30` don't show as `30.000000`.
Percentage Calculator Use Cases
- Calculating a discount, tax, or tip amount before totaling a bill
- Finding a percentage-based share of a budget, commission, or bonus
- Checking a test or assignment score expressed as a percentage of total points
Common Mistakes
- Mixing up which value is the percentage and which is the base number.
- Forgetting that a percentage over 100% is valid and simply produces a result larger than the base.
Tips
- If you instead know the result and need to find the original number, use the Reverse Percentage Calculator.
- If you're comparing two numbers to find the percentage change between them, use the Percentage Change Calculator instead.