Percentage Calculator
Three ways to calculate percentages — pick the tab that matches your question.
How to Use This Calculator
"X% of Y" tab
The default tab. Enter a percentage and a number — the calculator shows the result. Example: what is 15% of 200? Answer: 30. Use this for tips, discounts, tax amounts, or any "how much is X% of Y?" question.
"X is what % of Y?" tab
Enter two numbers — the part and the whole. The calculator tells you what percentage the first is of the second. Example: 30 is what % of 200? Answer: 15%. Use this for grades, completion rates, or comparing part to whole.
"% Change" tab
Enter an old value and a new value. The calculator shows the percentage increase or decrease. Example: from 80 to 100? That's a 25% increase. Use this for price changes, salary changes, or any before-and-after comparison.
Share your result
Every input is encoded in the URL. Click Share, send the link — they'll see your exact numbers. No re-entering, no screenshots.
The Formula
Each tab uses a different formula:
Where:
- X = the percentage or the part
- Y = the number or the whole
- Old = the original value
- New = the updated value
- |Old| = absolute value of the original (handles negative starting values)
A positive % change means an increase; a negative % change means a decrease.
Example
Three everyday scenarios
Tab 1 — "X% of Y": You want to leave a 15% tip on a $200 dinner.
Tab 2 — "X is what % of Y?": You scored 30 out of 200 points on a quiz.
Tab 3 — "% Change": Your rent went from $1,800 to $1,950.