How to use the Percentage Calculator
- 1
Choose the calculation you need from the four cards.
- 2
Type your numbers into the fields — results appear instantly.
- 3
Read the formula under each result to see how it was calculated.
- 4
Use the copy button to copy the answer.
Features & benefits
Four calculators in one
X% of Y, X is what % of Y, percentage change, and add or subtract a percentage.
Shows the formula
Every result includes the equation used, which is ideal for homework and reports.
Decimal friendly
Accepts decimals and negative numbers and formats large results clearly.
Instant results
No calculate button needed — answers update as you type.
Percentage formulas explained
“Per cent” means “per hundred”. To find X% of Y, multiply Y by X and divide by 100: 15% of 80 is 80 × 15 ÷ 100 = 12. To find what percentage X is of Y, divide X by Y and multiply by 100.
Percentage change compares a new value with an old one: (new − old) ÷ |old| × 100. Going from 50 to 65 is a 30% increase. Note that a 50% decrease followed by a 50% increase does not bring you back to the start — 100 becomes 50, then 75.
Frequently asked questions
How do I calculate a percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. Use the “Percentage change” card to do this automatically.
What's the difference between percentage and percentage points?
If a rate rises from 4% to 6%, that is an increase of 2 percentage points but a 50% relative increase.
Can the original value be zero?
Percentage change from zero is undefined, because you cannot divide by zero. The calculator will tell you when this happens.