Solve everyday percentage questions. This free percentage calculator finds a percent of a number, works out what percent one number is of another, and calculates percentage increase or decrease, with the working shown.
Find a percentage of a number – for example, what is 15% of 200?
Find what percentage one number is of another – for example, 30 is what % of 200?
Find the percentage increase or decrease from one value to another – for example, from 200 to 250.
Percent means “per hundred.” To find a percentage of a number, multiply by the percent and divide by 100. To express one number as a percentage of another, divide and multiply by 100.
How the Percentage Calculator Works
This calculator solves three everyday percentage questions in one place: finding a percent of a number, figuring out what percent one number is of another, and working out the percentage increase or decrease between two values. Each mode uses its own simple formula built around the idea that “percent” means “per hundred.”
Formula: For “percent of a number”: result = n × p ÷ 100. For “X is what % of Y”: percent = (x ÷ y) × 100. For “percentage change”: change % = ((b − a) ÷ a) × 100, where a negative result means a decrease and a positive result means an increase.
- p — the percent value you enter in “% of a number” mode
- n — the number you’re finding that percent of
- x — the number you’re expressing as a percentage in “X is what % of Y” mode
- y — the reference total in that same mode
- a — the starting (“From”) value in “% change” mode
- b — the ending (“To”) value in “% change” mode
Example Scenarios
| Mode | Input A | Input B | Result |
|---|---|---|---|
| % of a number | 15% | 200 | 30 |
| % of a number | 8% | 50 | 4 |
| X is what % | 30 | 200 | 15% |
| X is what % | 45 | 180 | 25% |
| % change | 200 (from) | 250 (to) | +25% |
| % change | 80 (from) | 60 (to) | -25% |
Percentage Calculator FAQ
How do I calculate what 15% of a number is?
Multiply the number by 15 and divide by 100, or equivalently multiply by 0.15. In “% of a number” mode, just enter 15 in the percent field and your number in the “of” field, and the calculator does the multiplication and division for you instantly.How is “X is what percent of Y” different from percentage change?
“X is what percent of Y” asks what share one number represents of another at a single point in time, like a score out of a total. Percentage change instead compares two values across time or across a shift — an original and a new value — to show how much it grew or shrank.Why does percentage change come out negative when a value decreases?
The formula (new − original) ÷ original × 100 produces a negative number whenever the new value is smaller than the original, since new minus original is negative. That negative sign is what signals a decrease rather than an increase in the result.How is this different from a dedicated percentage change calculator?
This calculator bundles percentage change in as one of three modes alongside “percent of a number” and “X is what percent of Y,” useful when you’re not sure in advance which calculation you need. A calculator built solely around percentage change may offer more detail specific to that one comparison.How do I find what percentage one value is of a total?
Switch to “X is what % of Y” mode, enter the part in the first field and the total in the second. For example, if you scored 30 out of 200 points, entering 30 and 200 shows the result is 15%.Can I use this for tips, discounts, or grade percentages?
Yes. Use “% of a number” to calculate a tip or discount amount (like 20% of a $50 bill), and “X is what % of Y” to work out a grade, such as how many points out of a total you scored as a percentage.Related Calculators
If you’re specifically comparing an original value to a new one, the dedicated percentage change calculator goes deeper into that single calculation, while the aggregate percentage calculator and attendance percentage calculator apply the same percent math to grades and class attendance.