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이 도구는 브라우저에서 실행됩니다. 입력값, 파일, 생성된 값은 이 기기에 남습니다. 즐겨찾기와 최근 사용한 도구를 이용하더라도 로컬 저장소에는 도구 이름만 저장되며, 비밀번호나 문서, QR 내용은 절대 저장되지 않습니다. 자세한 내용은 개인정보처리방침을 확인하세요.

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What this tool does

The Percentage Calculator answers three questions: what is X% of Y, what percent X is of Y, and what a number becomes after a percent increase or decrease. Use it for a grade, a share of a total, or a quick price change. A sale price, sales tax, and a tip each have their own calculator, because those jobs start from a price and a rate rather than these three patterns.

How to use

  1. Choose What is X% of Y?, X is what percent of Y?, or Increase or decrease.
  2. Enter the two numbers. For a percent of a number, X is the percent and Y is the number. For “what percent,” X is the part and Y is the whole. For a change, X is the percent and Y is the starting number.
  3. If you chose Increase or decrease, pick Increase or Decrease.
  4. Press Calculate. The large number is the result. The lines under it show the label and the arithmetic. Press Reset to clear the fields.

Examples

  • What is 15% of 80?

    Choose What is X% of Y? Enter 15 as Percentage (X) and 80 as Number (Y). Calculate shows 12. The detail line is 15 ÷ 100 × 80, and the label is 15% of 80.

  • 12 is what percent of 40?

    Choose X is what percent of Y? Enter 12 as Value (X) and 40 as Whole (Y). Calculate shows 30%. The detail line is 12 ÷ 40 × 100, and the label is 12 is this percent of 40.

  • Increase 200 by 10%

    Choose Increase or decrease, leave Direction on Increase, and enter 10 as Percent change (X) and 200 as Starting number (Y). Calculate shows 220. It also shows Amount added: 20, and the detail 200 + (10 ÷ 100 × 200).

How it works

A percentage is a number out of 100. “X% of Y” multiplies Y by X ÷ 100. “X is what percent of Y” divides X by Y and multiplies by 100. An increase adds that fraction to the starting number. A decrease subtracts it. The page rounds the arithmetic to 10 decimal places, then shows up to 6 decimal places.

Percentage points and percent are different questions

A rate that moves from 10% to 12% has risen by 2 percentage points. The relative change is 2 ÷ 10 × 100, which is 20%. Both sentences are true, and they are not interchangeable.

This page does not convert one into the other for you. If you already have the gap, use “what percent”: 2 is 20% of 10, so Calculate shows 20%. If you want the new rate after adding 20% of 10, use Increase: 10 increased by 20% shows 12, with 2 added. For two finished values, such as 80 then 100, use the Percentage Change Calculator.

Discount, tax, and tip use other calculators

A 25% discount on 80 takes 20 off and leaves 60. Decrease mode can do that arithmetic: enter 25 and 80, choose Decrease, and Calculate shows 60, with Amount subtracted: 20. The detail line is 80 − (25 ÷ 100 × 80).

The Discount Calculator is built for a price and a percent off, and it rejects a discount above 100%. The Sales Tax Calculator adds a rate to a price. The Tip Calculator splits a bill by a tip percent and a number of people. Use those pages when the question is a receipt, not a bare percent.

Zero, order, and symbols

0% of 50 is 0. The detail line is 0 ÷ 100 × 50. Asking what percent 5 is of 0 is rejected. The page says: The second number cannot be 0 when finding a percentage.

The order of the numbers is the question. 15% of 80 is 12, and 80% of 15 is also 12, but 12 is 15% of 80 and 12 is 80% of 15. Those are different “what percent” results. Enter 12 and 80 to see 15%. Enter 12 and 15 to see 80%.

Type plain numbers. A dollar sign or a percent sign in the field is invalid input. Decimals are allowed, so 12.5% of 80 is 10.

Privacy

The numbers stay in this browser tab. Calculate runs on the page. The values are not posted to a server and are not written to local storage. If you accept analytics cookies, the visit can be counted. The numbers you type are not part of that measurement.

Tips

  • Write the question in one sentence before you pick a mode. “15% of 80” and “15 is what percent of 80” are different jobs.
  • On an increase or decrease, X is the percent and Y is the starting number. Swapping them applies the percent to the wrong value.
  • Use Decrease when you want the number left after a percent is taken off. The large result is the new amount. The amount subtracted is a separate line.
  • Check a round case first. 10% of 50 is 5. If that mental check fails, the mode or the field order is wrong.

Limitations

This page only calculates a percent of a number, one number as a percent of another, or a percent increase or decrease. It does not look up a tax rate, and it does not split a tip. Dividing by zero is rejected in the “what percent” mode. A result is the arithmetic of the numbers you enter. It is not financial, tax, or grading advice.

See the disclaimer for what these tools do not cover.

FAQ

How do I calculate a percentage of a number?
Choose What is X% of Y? Put the percent in X and the number in Y, then press Calculate. 15% of 80 is 12, from 15 ÷ 100 × 80.
How do I find what percent one number is of another?
Choose X is what percent of Y? Put the part in X and the whole in Y. 12 out of 40 is 30%, from 12 ÷ 40 × 100. The whole cannot be 0.
How do I increase or decrease a number by a percent?
Choose Increase or decrease. Put the percent in X and the starting number in Y, then pick Increase or Decrease. Increasing 200 by 10% shows 220, with 20 added. Decreasing 80 by 25% shows 60, with 20 subtracted.
What is the difference between percent and percentage points?
Percentage points are a simple subtraction of two rates. From 10% to 12% is 2 percentage points. Percent is the relative change: 2 is 20% of 10. This calculator does not switch those two ideas automatically.
What happens if I use 0?
0% of a number is 0. Finding what percent a number is of 0 is not possible, so the tool asks for a different second number. The message is: The second number cannot be 0 when finding a percentage.
Is my input sent to a server?
No. The numbers you type are calculated in this browser tab. Tools Star Hub does not send those numbers to a server or save them in local storage.
Is the Percentage Calculator free?
Yes. You can find a percent of a number, what percent one number is of another, or a percent increase or decrease here without paying or creating an account.

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