What is 21 Percent of 100?
21% of 100 = 21
Step by step
- Turn the percentage into a decimal: 21 ÷ 100 = 0.21
- Multiply: 0.21 × 100 = 21
How the answer is worked out
“Percent” means “per hundred”, so 21% is 21 out of every 100, or 0.21 as a decimal. Taking 21% of 100 means multiplying 100 by 0.21, which gives 21.
21 is the 21% share of 100. The remaining 79% is 79, and the two parts add back up to 100.
Why calculate this?
Taking a percentage of a number is how discounts, tips, tax and interest are worked out.
- Discounts: 21% off an item priced $100 saves $21, so you pay $79.
- Tips: a 21% tip on a bill of $100 is $21, so the total is $121.
- Interest: simple interest of 21% a year on $100 earns $21 in one year and $105 over five years.
- Tax: a sales tax of 21% on a price of $100 adds $21, so the price including tax is $121.
A quicker way
Use 10% and 1%: 10% of 100 is 10 and 1% is 1. 21% is 2 × 10% + 1 × 1% = 20 + 1 = 21.
Swap the numbers if that is easier: 21% of 100 is always the same as 100% of 21, because both are 21 × 100 ÷ 100.
Check the answer
Work backwards: 21 ÷ 100 × 100 = 21%. Getting 21% back shows the answer is right.
Rounding
Rounded to a whole number the result is 21, to one decimal place 21.0 and to two decimal places 21.00. Round only at the end: rounding halfway through a calculation can change the last digit.
The formula explained
result = percentage ÷ 100 × number. Dividing the percentage by 100 turns it into a decimal multiplier, so 25% becomes 0.25 and 150% becomes 1.5. Multiplying the number by that decimal gives the share.
Another worked example: 5% of 67
- Turn the percentage into a decimal: 5 ÷ 100 = 0.05
- Multiply: 0.05 × 67 = 3.35
Common percentages of 100
10% of 100 is 10, 20% is 20, a quarter (25%) is 25, half (50%) is 50 and three quarters (75%) is 75. Knowing these makes it easy to estimate any other percentage of 100 in your head.
Adding and taking away 21%
Increasing 100 by 21% gives 121 and decreasing it by 21% gives 79. These do not cancel out: raising 100 by 21% and then lowering the result by 21% ends at 95.59, because the second 21% is taken of a bigger number.
Finding the original number
If 21 is 21% of something, divide by 0.21 to get it back: 21 ÷ 0.21 = 100. This is how you work out a price before tax or a full amount from a share of it.
Other ways to ask this
The same calculation is often asked in other words. All of these have the answer above:
- What is 21 percent of 100?
- 21% of 100
- 21 percent times 100
- Find 21% of 100
- How much is 21 per cent of 100?
Terms used on this page
- Percentage: the rate, the number with the % sign.
- Base: the number you take the percentage of.
- Decimal multiplier: the percentage divided by 100.
- Mark-up and discount: adding or taking away a percentage of a price.
The answer in other forms
| Result | 21 |
|---|---|
| Remaining | 79 |
| 21% as decimal | 0.21 |
| 100 + 21% | 121 |
Related results
| 5% of 100 | 5% of 100 = 5 |
| 10% of 100 | 10% of 100 = 10 |
| 15% of 100 | 15% of 100 = 15 |
| 20% of 100 | 20% of 100 = 20 |
| 25% of 100 | 25% of 100 = 25 |
| 50% of 100 | 50% of 100 = 50 |
| 75% of 100 | 75% of 100 = 75 |
The other way round: 100% of 21
Doing it in a spreadsheet
In Excel, Google Sheets or Numbers type =21%*100 into any cell. Replace the numbers with cell references (for example A1 and B1) to reuse the formula for a whole column.
Common mistakes
Forgetting to divide the percentage by 100 makes the answer 100 times too big. Note that x% of y always equals y% of x.
Practice examples
| 5% of 67 | Show answer5% of 67 = 3.35 |
| 15% of 73 | Show answer15% of 73 = 10.95 |
| 29% of 72 | Show answer29% of 72 = 20.88 |
| 89% of 31 | Show answer89% of 31 = 27.59 |
| 36% of 3 | Show answer36% of 3 = 1.08 |
| 37% of 67 | Show answer37% of 67 = 24.79 |
| 25% of 48 | Show answer25% of 48 = 12 |
| 39% of 51 | Show answer39% of 51 = 19.89 |
| 49% of 74 | Show answer49% of 74 = 36.26 |
| 31% of 63 | Show answer31% of 63 = 19.53 |
How this answer was calculated
The result is worked out from the numbers in this page's address when the page is opened, using exact arithmetic wherever possible and rounding only for display. Nothing is copied from a printed table. If you think an answer is wrong, please tell us through the contact page and we will check it.
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Questions
What is 21 Percent of 100?
21% of 100 is 21. Formula, steps and practice examples.
What is 21% off 100?
79. Taking 21% off leaves 79% of 100.
What is 100 plus 21%?
121. Adding 21% is the same as multiplying by 1.21.
What is 21% of 100 as a fraction?
21/100 × 100 = 2100/100, which simplifies to 21/1.
How do I find 21% of a number on a calculator?
Multiply the number by 0.21. For 100 that is 100 × 0.21 = 21. On many calculators you can also type 100 × 21 %.