Percentage Calculator
Three calculators in one: X% of Y, X is what percent of Y, and percentage increase/decrease.
How to use this tool
Pick a mode
Choose X% of Y, “X is what % of Y”, or percentage change between two values.
Enter your numbers
Decimals work fine. Results update as you type.
Read the answer
A big clear result plus the full working shown underneath.
Frequently asked questions
What are the three modes?
“X% of Y” finds a portion (20% of 200 = 40). “X is what % of Y” finds the share (40 is 20% of 200). “% change” finds increase or decrease between two numbers.
How is percentage increase calculated?
Subtract the old value from the new value, divide by the old value, and multiply by 100. A negative result means a decrease.
Can I use decimals?
Yes — all fields accept decimals, so 12.5% of 80 works fine.
Is my input sent anywhere?
No. Everything is calculated locally in your browser.
Why do I get so many decimal places?
Results are rounded to a sensible precision automatically — trailing zeros are trimmed so 40 stays 40, not 40.0000.