Calculating a discount
Before
Item was 25% off, original price $80
After
Discount is $20, final price $60
The math is simple, but I've seen people mess it up. This tool shows both the savings and the final price.
All Tools
Percentage Calculator – Percentages and Change
I built this because I kept doing percentage math in a scratch file, getting it slightly wrong, and having to redo it. Pick your calculation type, enter the numbers, get the answer. Handles the four calculations that come up in real life — percent of a number, what percent one number is of another, percent increase, and percent decrease.
100% free, no signup
What is X% of Y?
% of
50
X is what % of Y?
is % of
12.50%
% change from X to Y
→
+25.00%
Save calculation history + export
Your files are processed in your browser and never uploaded to any server.
A note from me
The percentage change formula that trips people up: it's `(new - old) / old * 100`, not `(new - old) / new`. If a price goes from $100 to $80, that's a 20% decrease — not 25%. I see this mistake in business reports all the time. This tool uses the correct formula, but it's worth knowing so you can sanity-check the output.
— Mirza Noman Baig
How to use this tool
- 1Choose the calculation type.
- 2Enter your values.
- 3See the result instantly.
- 4Use the answer for discounts, comparisons, or reports.
Real results from testing
These are actual measurements from using this tool, not estimates.
Business growth report
Before
Revenue went from $45,000 to $58,000
After
That's a 28.9% increase
Used the correct formula: (58-45)/45 = 28.9%. Easy to get wrong if you divide by the new value.
Exam score improvement
Before
Student went from 62% to 78%
After
That's a 25.8% improvement
Useful for parent-teacher meetings when you need to explain progress with real numbers.
Percentage Calculator features
Four calculation types
Percent of a number, what percent one number is of another, increase, and decrease.
Correct formula
Uses the standard formula for percentage change — denominator is the original value.
Instant results
See the answer as soon as you enter the numbers.
Runs locally
No uploads, no accounts. Safe for financial numbers.
Frequently asked questions
What's the formula for percentage change?+
It's (new - old) / old × 100. The denominator is always the original value, not the new one.
Can this calculate discounts?+
Yes. Enter the original price and the discount percentage, and the tool gives you the discounted price.
Can percentage change be negative?+
Yes. A negative number means the value decreased. A positive number means it increased.
Is my input stored?+
No. Everything runs in your browser. Your numbers never leave your device.
Can it handle multiple calculations at once?+
Each calculation type is separate. Switch between them as needed — the tool keeps the last value.