Percentage calculator
Three quick tools in one — find a percentage of a number, what percent one number is of another, and percentage change.
What is X% of Y?
X is what percent of Y?
Percentage increase / decrease
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Percentage formulas
- X% of Y = (X ÷ 100) × Y. Use this when you know a percentage and a total, and need the actual amount it represents, for example a discount amount or a tip amount.
- X as a percent of Y = (X ÷ Y) × 100. Use this when you have two raw numbers and want to know what share one is of the other, for example a test score out of total marks.
- Percent change = ((New − Old) ÷ Old) × 100. Use this when a number has moved from one value to another and you want to know how big that move was in percentage terms, for example a salary change or a price change.
The donut chart above the first tool shows exactly what your chosen percentage looks like as a slice of the whole, a quick visual check that the number "feels right" before you use it.
Worked example, X% of Y: what is 20% of 80? Convert 20% to a decimal (20 ÷ 100 = 0.2), then multiply by 80: 0.2 × 80 = 16. So 20% of 80 is 16.
Worked example, X is what percent of Y: 12 is what percent of 60? Divide 12 by 60 to get 0.2, then multiply by 100: 0.2 × 100 = 20. So 12 is 20% of 60.
Worked example, percentage increase: a jacket goes from $50 to $65. Step one, find the difference: $65 − $50 = $15. Step two, divide the difference by the original value: $15 ÷ $50 = 0.3. Step three, multiply by 100 to get a percentage: 0.3 × 100 = 30%. So the price rose by 30%. If the jacket had instead dropped from $65 to $50, the same steps give ($50 − $65) ÷ $65 × 100 = −23.08%, a 23.08% decrease. Notice the percentage decrease is smaller in magnitude than the increase even though the dollar amount is identical, because percentage change is always measured against the starting value.
X% of common totals, quick reference
| Total | 10% | 15% | 20% | 25% |
|---|---|---|---|---|
| 50 | 5.0 | 7.5 | 10.0 | 12.5 |
| 100 | 10.0 | 15.0 | 20.0 | 25.0 |
| 200 | 20.0 | 30.0 | 40.0 | 50.0 |
| 500 | 50.0 | 75.0 | 100.0 | 125.0 |
Everyday uses for percentages
- Shopping discounts: "X% of Y" tells you exactly how much you save on a sale price. A $40 shirt marked 25% off saves you 0.25 × $40 = $10, so you pay $30. If a second discount stacks on top, say an extra 10% off the already-reduced $30, that second discount applies to $30, not the original $40: 0.10 × $30 = $3 off, for a final price of $27, not $26 as a naive "35% off $40" calculation would suggest.
- Restaurant tips: a 18% tip on a $52 bill is 0.18 × $52 = $9.36. See our dedicated tip calculator for a faster, purpose-built version that also handles splitting the bill.
- Exam scores: "X is what percent of Y" converts a raw score into a percentage grade. Scoring 42 out of 50 on a test is (42 ÷ 50) × 100 = 84%, which most grading scales would mark as a B.
- Sales tax: a 7% sales tax on a $120 purchase adds 0.07 × $120 = $8.40, bringing the total to $128.40.
- Pay rises and price changes: the increase/decrease tool shows the exact percentage change between two numbers, e.g. how to calculate a percentage increase.
Percentages appear everywhere in daily life: discounts while shopping, tips at restaurants, tax rates, exam scores and interest rates. Bookmark this page for instant answers.
Frequently asked questions
How do I calculate X% of Y?
Multiply Y by X and divide by 100, e.g. 15% of 200 = (15 ÷ 100) × 200 = 30.
How do I find what percent X is of Y?
Divide X by Y and multiply by 100, e.g. 30 is 20% of 150.
How do I calculate percentage increase or decrease?
(New − Old) ÷ Old × 100. A positive result is an increase; negative is a decrease.
How do I calculate percentage change when the numbers could be negative?
The same formula works, but be careful with the sign of the "Old" value. If a business's profit goes from -$10,000 to $5,000, the change is ($5,000 − (−$10,000)) ÷ (−$10,000) × 100 = −150%. The negative result looks odd next to what is clearly an improvement, so in cases where the starting value is negative or zero it's often clearer to describe the change in plain dollar or unit terms instead of as a percentage.
What's the difference between percentage points and percent?
A percentage point is a simple difference between two percentages, while percent describes a relative change. If interest rates move from 5% to 7%, that's a 2 percentage point increase, but a 40% relative increase (2 ÷ 5 × 100 = 40%). The two numbers describe the same move but mean very different things, so it matters which one a headline or report is using.
Can stacked percentage discounts just be added together?
No — this is one of the most common percentage mistakes. Two 20% discounts applied one after another give 36% off total, not 40%, because the second discount applies to the already-reduced price. See our discount calculator for the full stacking math.
A note on common mistakes
The most frequent percentage error is confusing "percent of" with "percent change," or applying a percentage to the wrong base number — like calculating a discount on the original price when a second, stacked discount should apply to the already-reduced price instead. When in doubt, write out which number is your "whole" (the 100% reference point) before doing the maths; most mistakes come from losing track of that.