Free Percentage Calculator
Three percent calculators in one: X% of Y, X as a percentage of Y, and percent change. Answers update as you type.
What is X% of Y?
X is what percent of Y?
Percent change from X to Y
How to use the percentage calculator
- X% of Y: enter the percent and the value — perfect for discounts, tips, and tax.
- X is what % of Y: enter the part and the whole — ideal for grades, progress, and stats.
- Percent change: enter the old and new values — great for price changes and growth.
Percentage math, demystified
Percentages trip people up because the same symbol answers three different questions. "20% of 150" asks for a slice of a known whole — multiply 150 by 0.20 to get 30. "30 is what percent of 150" works backwards — divide 30 by 150 to get 0.20, or 20%. And "percent change" compares two values over time: subtract the old from the new, divide by the old, and multiply by 100. A $100 item rising to $130 is a 30% increase; falling to $70 is a 30% decrease. Two traps to avoid: first, "percentage points" are not "percent" — going from 20% to 25% is a 5-point rise but a 25% relative increase. Second, reversing a discount does not work symmetrically: a 20% discount followed by a 20% increase does not return to the original price, because the second percent applies to a smaller base. When in doubt, run the numbers here instead of guessing.
Frequently asked questions
How do I calculate X percent of Y?
Convert the percent to a decimal and multiply: 20% of 150 = 0.20 × 150 = 30. The first calculator above does it instantly.
What is the difference between percent change and percentage points?
Percent change is relative: from 20% to 25% is a 25% increase. Percentage points are absolute: the same move is 5 percentage points. News about rates and polls usually means points.
How do I reverse a percentage discount?
Divide by (1 − discount). To undo a 20% discount on a $80 sale price: 80 ÷ 0.80 = $100 original price.
Can percent change be over 100%?
Yes. Going from 50 to 200 is a 300% increase — the value tripled, which is the original 100% plus 200% more.