Percentage Increase & Decrease Calculator
Find the percentage increase or decrease between an old value and a new value, or choose either of the other modes to calculate a percentage of a number. For a change, use the original amount as X and the new amount as Y.
Please enter valid numbers (Y cannot be 0).
How to Use the Percentage Calculator
- Choose the calculation type that matches your question.
- Enter the two numbers involved in the problem.
- Calculate to see the percentage or the resulting value.
- Use the change mode when comparing an old figure with a new figure.
Pick the calculation type first: “What is X% of Y?” finds a share of a number, “X is what % of Y?” finds a percentage, and the increase and decrease types compare an old value with a new one. Then fill in the two boxes. The labels change to match the type you chose. For a change, enter the old value in X and the new value in Y. The old value cannot be zero.
Percentage Calculator Formula Explained
X percent of Y equals Y times (X divided by 100). “X is what percent of Y” equals (X divided by Y) times 100. Percentage change equals ((new minus old) divided by old) times 100. A positive change is an increase; a negative change is a decrease. Percentage points—the arithmetic difference between two percentages—are not the same as percentage change and should not be confused in reporting.
Each type uses one simple formula. X% of Y is X ÷ 100 × Y. “X is what % of Y” is X ÷ Y × 100. Percentage increase is (new − old) ÷ old × 100, and percentage decrease is (old − new) ÷ old × 100. Both change formulas divide by the old value. That is why going from 80 to 100 is a 25% increase, but going back from 100 to 80 is a 20% decrease. Results are rounded to two decimal places.
Percentage Calculator Example Calculation
A price rising from €80 to €100 is a €20 change and a 25% increase relative to the original. A rate moving from 10% to 15% is a 5 percentage-point rise but a 50% relative increase—use the language that matches your report.
Worked example: choose “X is what % of Y?” with X = 30 and Y = 120. The result is 25.00%. Next, choose “Percentage increase from X to Y” with X = 80 and Y = 100. The result is 25.00%. Choose “Percentage decrease from X to Y” with X = 100 and Y = 80, and the result is 20.00%. For “What is X% of Y?”, 15% of 200 is 30.
When to use this tool
Use this for discounts, VAT checks, exam scores, KPIs and any everyday percentage change across business and study work.
Key Features & Benefits of This Percentage Calculator
- Four calculations in one — X% of Y, X is what % of Y, percentage increase and percentage decrease.
- Labels follow your choice — the input labels change with the calculation type, so you always know what to enter.
- Change measured from the old value — going from 80 to 100 is a 25% increase, while going back from 100 to 80 is a 20% decrease.
- Two-decimal results — answers are rounded to two decimal places.
- Instant, free and private — runs entirely in your browser, no sign-up, nothing stored.
Percentage Calculator — FAQs
What is the difference between percent change and percentage points?
If a rate moves from 10% to 15%, that is a 5 percentage-point rise but a 50% relative increase. Use the language that matches the claim you want to make.
Can percentage change exceed 100%?
Yes. Doubling is a 100% increase; tripling is a 200% increase.
How do I reverse a percentage increase?
To undo an increase of p%, divide by (1 + p/100). To undo a decrease of p%, divide by (1 − p/100).
Why does order matter in successive percentages?
A 20% increase followed by a 20% decrease does not return to the start; you end lower because the decrease applies to a larger base.
What is the percent increase from 50 to 70?
It is 40%: the increase is 20, and 20 ÷ 50 × 100 = 40. Divide by the original 50, not the final 70.
How do I calculate a 5% increase?
Multiply the starting amount by 1.05. For example, 200 × 1.05 = 210. The increase itself is 10.
Percentage change between two numbers
| Old value | New value | Calculation | Answer |
|---|---|---|---|
| 50 | 70 | (70 − 50) ÷ 50 × 100 | 40% increase |
| 80 | 100 | (100 − 80) ÷ 80 × 100 | 25% increase |
| 100 | 80 | (100 − 80) ÷ 100 × 100 | 20% decrease |
| 250 | 0 | (250 − 0) ÷ 250 × 100 | 100% decrease |
Use increase mode for an increase and decrease mode for a decrease. A negative answer means the values moved in the opposite direction to the mode you selected. A starting value of zero has no ordinary percentage-change result because division by zero is undefined.
Increase a number by a percentage
To increase 52 by 14%, first choose “What is X% of Y?” and enter X = 14 and Y = 52. The increase is 7.28; add that to 52 to get 59.28. In a single formula: new value = original value × (1 + percentage ÷ 100).
To reduce a value, use original value × (1 − percentage ÷ 100). A 15% decrease from 200 leaves 170. Increasing by 15% adds 15% to the original; increasing to 115% means making the final value 115% of the original.