What is a percentage calculator?
A percentage calculator answers the everyday questions that involve "percent": what is 18% GST on a bill, what percentage of the class passed, how much did a price rise, what will a salary be after a 7% hike. Each needs a slightly different formula, and mixing them up is a common mistake.
This page puts all four calculations side by side, each with its own pair of boxes, so you pick the question rather than the formula. Results update as you type, accept decimals and negative numbers, and can be copied with one click. The link saves every number you've entered.
How to use the Percentage Calculator
1.Find the right question
Each box answers one common question, worded the way you'd ask it.
2.Type your two numbers
Answers appear as you type. Negative numbers and decimals are fine.
3.Copy the answer
Press Copy next to any result, or share the link to keep all four sets of numbers.
Example: four questions, four answers
The default numbers on this page:
- 15% of 2,400
- 360
- 360 is what % of 2,400
- 15%
- Change from 1,200 to 1,500
- 25% increase
- 1,500 increased by 12%
- 1,680
change % = (new − old) ÷ |old| × 100
The first two are the same relationship asked in opposite directions.
The four formulas
X% of Y = X ÷ 100 × Y. What percent X is of Y = X ÷ Y × 100. Percentage change from A to B = (B − A) ÷ |A| × 100, positive for an increase and negative for a decrease. Increasing Y by X% = Y × (1 + X ÷ 100); decreasing it multiplies by (1 − X ÷ 100).
A percentage change isn't symmetric. Going from 1,200 to 1,500 is a 25% increase, but going back from 1,500 to 1,200 is a 20% decrease, because the starting value differs.
Frequently asked questions
How do I calculate 15% of 2,400?
Multiply 2,400 by 15 and divide by 100: 360.
How do I work out a percentage increase?
Subtract the old value from the new one, divide by the old value and multiply by 100. 1,200 to 1,500 is a 25% increase.
Why doesn't a 10% rise followed by a 10% fall get back to the start?
The fall is 10% of a bigger number. 100 rises to 110, then falls by 11 to 99.
What is percentage point change?
The plain difference between two percentages. A rate moving from 6% to 8% rose by 2 percentage points, which is a 33% increase.
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