Percentage Calculator
Percent of a number, what percent of, and percentage increase or decrease.
About This Tool
The Percentage Calculator handles the three most common percentage questions: finding a percent of a number, working out what percent one number is of another, and calculating the percentage increase or decrease between two values. Each block updates live as you type.
It is useful for discounts, marks, tips, tax, and growth figures, and runs entirely in your browser.
- check_circleFind X% of a number
- check_circleFind what percent one number is of another
- check_circleCalculate percentage increase or decrease
- check_circleLive, browser-based calculation
The three percentage questions, and how they differ
Almost every percentage problem is one of three. What is X percent of Y multiplies: 18 percent of 2,400 is 0.18 x 2400 = 432. X is what percent of Y divides: 432 out of 2,400 is 432/2400 = 18 percent. And percentage change compares two numbers: (new minus old) divided by old, so a price moving from 2,400 to 2,832 is 432/2400 = an 18 percent increase.
Identifying which one you have is most of the work. The giveaway is what you already know: if you know the whole and the rate, you are multiplying; if you know the part and the whole, you are dividing; if you have two comparable figures from different times, it is a change.
Percentage points are not percentages
This distinction shows up constantly in news reporting and financial documents, and confusing the two produces errors of an order of magnitude. If an interest rate rises from 4 percent to 6 percent, that is a rise of 2 percentage points, and also a rise of 50 percent. Both statements are true and they describe the same event with very different emotional weight.
The convention is to use percentage points whenever both figures are themselves percentages, and to reserve percent for a proportional change. A loan rate that goes from 8.5 to 9.0 has risen 0.5 percentage points, roughly 5.9 percent. When reading a report that says a rate rose "by 15 percent", check which is meant before acting on it.
Why a discount and a markup of the same size do not cancel
Percentages apply to whatever the current base is, and the base changes as you go. Take 2,000, cut it by 20 percent to 1,600, then add 20 percent back: you get 1,920, not 2,000. The reduction was 20 percent of 2,000 while the increase was 20 percent of 1,600. This is why a stock that falls 50 percent needs a 100 percent gain to recover, and why stacked discounts of 30 percent and 20 percent give 44 percent off, not 50.
Two Indian everyday cases follow from this. Reversing GST from an inclusive price is a division, not a subtraction: at 18 percent, the base is the total divided by 1.18, so 1,180 inclusive contains 180 of tax, and subtracting 18 percent of 1,180 would wrongly give 967.60. Salary hikes compound the same way, so two consecutive 10 percent increases produce 21 percent, not 20.
Percentage results that surprise people
| Operation | Starting value | Result |
|---|---|---|
| -20% then +20% | 2,000 | 1,920, not 2,000 |
| -50%, then recover | 2,000 | Needs +100% to return to 2,000 |
| 30% off then a further 20% off | 1,000 | 560, a 44% total discount |
| Remove 18% GST from 1,180 | 1,180 inclusive | 1,000 base and 180 tax |
| +10% twice | 50,000 | 60,500, a 21% rise |
Frequently Asked Questions
How do I find a percentage of a number? expand_more
Multiply the number by the percentage and divide by 100. For example, 20% of 500 is 500 × 20 / 100 = 100. The first block does this for you.
How is percentage change calculated? expand_more
Percentage change is (new − old) / old × 100. A positive result is an increase and a negative result is a decrease.
Is it free? expand_more
Yes. The calculator is free and runs in your browser.