Percentage Calculator
Find a percent of a number, compare part to whole, or measure percent change with the formula, steps, and a worked example shown.
Result
36
15% of 240 = 36
Quick Answer
To find a percent of a number, divide the percent by 100 and multiply by the number: 15 percent of 240 is 0.15 times 240, which is 36. To find what percent one number is of another, divide the part by the whole and multiply by 100. This calculator runs both, plus percent change, and shows every step.
What A Percentage Calculator Does And How It Works
The Percentage Calculator is a free math tool that works with percentages three ways. A percent means parts out of 100. This tool can find a percent of a number, find what percent one number is of another, or find the percent change from an old value to a new value. Each mode uses the same simple idea. It turns the percent into a decimal, compares a part with a whole, or compares a change with the starting value. A percent helps you compare numbers on the same 100-part scale. This helps with discounts, scores, tips, tax estimates, price changes, and any case where one number needs to be read against another. To find 15 percent of 240, the tool divides 15 by 100 and multiplies by 240 to give 36. The tool shows the answer and the method, so you can use the result and still check the math by hand.
The Percentage Calculator Formula And How It Is Applied
The tool uses three percent formulas, one for each mode.
- Percent of a number: result = (percent / 100) x value.
- Part as a percent: result = (part / whole) x 100.
- Percent change: result = ((new value - old value) / absolute old value) x 100.
In these formulas, the part is the amount you compare with a whole. The whole is the full amount. The old value is the starting number for a change.
A percent is not a unit. It is a way to compare. If the whole changes, the same percent can point to a new amount.
How To Use A Percentage Calculator In Clear Steps
Inputs
- Mode: choose percent of a number, part of a whole, or percent change.
- First value: enter the percent, part, or old value, based on the selected mode.
- Second value: enter the whole value, total, or new value, based on the selected mode.
Steps
- Pick the mode that matches your question.
- Enter both values in the labeled fields.
- Read the result in the result box.
- Check the visible formula and worked example below.
Percentage Calculator Example, Worked In Full
What is 15 percent of 240?
- Divide the percent by 100: 15 / 100 = 0.15.
- Multiply the decimal by the value: 0.15 x 240 = 36.
- Result: 15 percent of 240 is 36.
- Rounding: the result is a whole number, so no decimal rounding is needed.
15 percent of 240 is 36.
When A Percentage Calculator Gives The Right Answer
This tool is useful when a question compares one number with another. Use it for sale prices, tax estimates, tips, grades, score changes, and budget changes. It also helps when an answer should be shown as a percent or as a percent-based value.
In real terms, the tool is best for quick checks that still need clear working. A shopper can check a discount. A student can check a score. A small team can compare a value before and after a change. The method stays the same, even when the units change.
Percent questions also connect to the other basic math tools on this site. The math calculators hub lists each tool, the formula reference collects every formula in one place, and the glossary gives short definitions of common calculator terms.
Assumptions
- A percent means a value out of 100.
- The tool treats inputs as plain numbers with no fixed unit.
- Percent of a number mode converts the percent to a decimal before multiplying.
- Percent change uses the old value as the base.
- Results are rounded only for display.
The tool does not change the meaning of your unit. If you enter dollars, the answer is in dollars. If you enter points, the answer is in points. When the answer is a percent, the percent sign shows that the result is a share or a change.
Limitations
- The tool does not solve reverse percent questions.
- Percent change is not defined when the old value is zero.
- The tool does not add tax, discount, and tip in one combined step.
- Percentage points and percent change are different measures.
In Practice
The most common mistake is confusing percent change with percentage points. Going from 40 percent to 45 percent is a rise of 5 percentage points, but a 12.5 percent change. Decide which one your question needs before you read the result, because the two numbers are rarely the same.
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Frequently Asked Questions About Percentage Calculators
How do I find what percent one number is of another?
To find what percent one number is of another, divide the part by the whole, then multiply by 100. For 30 out of 120, that is (30 / 120) x 100, which is 25 percent. The X is what percent of Y mode runs this division for you and shows the answer in plain words.
What formula does a percentage calculator use?
A percentage calculator uses percent as a value out of 100, so it first divides the percent by 100. For percent of a number, it then multiplies that decimal by the value. The same out-of-100 idea drives the part-to-whole and percent-change modes.
How do I calculate a percentage increase or decrease?
The percent change mode compares the difference between the two values with the old value as the base. The formula is ((new value - old value) / absolute old value) x 100. A rise from 80 to 100 is (20 / 80) x 100 = 25 percent, and a negative result means a decrease.
Why is percent change undefined when the old value is zero?
Percent change needs a starting value to use as the base. When the old value is zero, the formula divides by zero. The tool shows a message instead of a number.
How do I work out a reverse percentage?
A reverse percent question starts with the final value and works back to the original whole. Divide the final value by the percent in decimal form. If a sale price of 80 is 80 percent of the full price, the full price is 80 / 0.80 = 100. This tool does not include a reverse mode, so use that division by hand.
Is percent change the same as percentage points?
No, percent change and percentage points measure different things and often give different numbers. Percent change compares movement from a base value. Percentage points measure the simple gap between two percents, such as 40 percent to 45 percent, which is a rise of 5 points but a 12.5 percent change.
Sources
Last updated: . Reviewed for accuracy against the formula shown above.