Percentage Calculator
This calculator separates several commonly confused percentage questions and shows the formula result with the selected values.
Calculate common percentage relationships
Choose a calculation such as X percent of Y, what percent X is of Y, or percentage change.
Processing mode: browser-only for this tool. The interface does not require a server upload to perform its transformation.
Start with a focused browser tool
This calculator separates several commonly confused percentage questions and shows the formula result with the selected values.
Designed for: Students, shoppers, analysts, and anyone checking everyday percentage arithmetic.
How to use this tool
Choose the operation and enter the numbers. The tool calculates a percentage of a value, a ratio as a percentage, or the change from an old value to a new value.
How the result is produced
The browser uses ordinary decimal arithmetic: percent of value is (percent / 100) × value; ratio percentage is part ÷ whole × 100; percentage change is (new − old) ÷ old × 100.
Test examples
15 percent of 200 is 30. 30 is 15 percent of 200. A change from 80 to 100 is a 25 percent increase relative to the original 80.
Limitations
Rounding is shown for readability and can differ from accounting or billing systems. A percentage change is undefined when the baseline is zero. This is arithmetic assistance, not financial, tax, medical, or legal advice.
Privacy and processing
The numbers are calculated locally in the browser and are not uploaded.
Related guide
The three percentage questions people often mix up
Related tools in this category
Documentation
- https://en.wikipedia.org/wiki/Percentage
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toFixed
This page describes the implementation shipped with the NOFYI Tool Factory. Review the interface output before using it in a production workflow.