Percentage Calculator — What is X% of Y, Increase & More
Four essential percentage calculations in one place. Whether you need to find a discount, check a test score, calculate a salary raise, or figure out VAT — get the answer instantly with the formula shown.
Use the hero calculator above for the most common task: finding what X% of Y equals. The three sections below cover every other percentage problem you're likely to face.
How to Use the Percentage Calculator
- Pick the right section — four calculators cover the four most common percentage problems.
- Enter your numbers — results update instantly as you type.
- Copy the result — click Copy to save it to your clipboard and add the calculation to your history.
The Four Percentage Calculations
What is X% of Y?
Use this when you know a percentage and want to find the actual amount it represents.
Formula: Result = (X ÷ 100) × Y
When to use: calculating discounts ("30% off $80"), tips ("15% of $45"), tax ("20% VAT on $120"), or commission ("5% of $3,000").
X is What Percent of Y?
Use this when you have two numbers and want to express the relationship as a percentage.
Formula: Percentage = (X ÷ Y) × 100
When to use: checking exam scores ("I got 72 out of 90 — what percentage is that?"), market share, survey response rates, or finding what portion one number is of a total.
Percentage Increase or Decrease from X to Y
Use this when comparing a before-value to an after-value to find the change.
Formula: % Change = ((Y − X) ÷ |X|) × 100
A positive result means an increase; a negative result means a decrease.
When to use: salary raises, price changes, revenue growth, population changes, or any "before and after" comparison.
Add or Subtract a Percentage from a Value
Use this when you know the starting number and want to apply a percentage change to it.
Formula (add): New value = X × (1 + Y ÷ 100) Formula (subtract): New value = X × (1 − Y ÷ 100)
When to use: applying discounts to prices, adding VAT or sales tax, calculating a salary after a raise, or finding a price after a markup.
Frequently Asked Questions
How do I calculate what percent X is of Y?
Divide X by Y and multiply by 100. For example, to find what percent 30 is of 120: (30 ÷ 120) × 100 = 25%. This tells you that 30 is 25% of 120. Use the "X is what % of Y?" calculator above — enter X as the part and Y as the whole.
How do I calculate percentage increase between two numbers?
Subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100. Formula: ((New − Old) ÷ |Old|) × 100. For example, from 80 to 100: ((100 − 80) ÷ 80) × 100 = 25% increase. Use the "Percentage increase or decrease" calculator above.
What is the difference between percentage increase and percentage difference?
Percentage increase compares a new value to a defined original (baseline), and the result is directional — it tells you whether values went up or down. Percentage difference has no defined baseline and uses the average of the two values; it is symmetric and always positive. Use percentage increase when you have a clear "before" and "after."
How do I add a percentage to a number?
Multiply the number by 1 + (percentage ÷ 100). For example, to add 20% to 500: 500 × (1 + 20/100) = 500 × 1.20 = 600. To subtract 15% from 200: 200 × (1 − 15/100) = 200 × 0.85 = 170. The "Add or subtract a %" section above handles both cases.
Can a percentage be greater than 100%?
Yes. If a value more than doubles, the percentage increase exceeds 100%. For example, growing from 50 to 150 is a ((150 − 50) ÷ 50) × 100 = 200% increase. Percentages over 100% are common in revenue growth, follower counts, and investment returns.
What is a reverse percentage calculation?
A reverse percentage finds the original value before a percentage was applied. If a price after a 20% increase is $120, the original price was $120 ÷ 1.20 = $100. If a price after a 30% discount is $56, the original price was $56 ÷ 0.70 = $80. Use the "add or subtract a %" section and rearrange the formula manually.
How do I calculate a discount?
Use the "add or subtract a %" section: enter the original price as X, the discount percentage as Y, and select "subtract". For example, a 25% discount on $80: $80 × (1 − 25/100) = $80 × 0.75 = $60. The calculator shows the discounted price directly.
Resources
- Khan Academy — Percentages — Clear, structured lessons on percentage fundamentals with practice problems.
- Wikipedia — Percentage — Mathematical definition and historical context for percentages.
