The fastest way: multiply, then move the decimal
To find a percentage of a number on a calculator, multiply the number by the percentage, then divide by 100. For example, to find 20% of 150: type 150, press the multiply button (×), type 20, press equals (=), then divide by 100. The answer is 30.
Most calculators let you skip the division step. After you multiply 150 × 20, you can press the percent button (%) instead of equals, and the calculator does the division for you automatically. The result appears as 30.
This method works the same way on a phone calculator, a basic four-function calculator, or a scientific calculator. The percent button is optional — dividing by 100 always gives you the right answer.
Key Takeaways
- Multiply the number by the percentage, then divide by 100 — or use the percent button (%) to skip the division step.
- To find 20% of 150, type 150 × 20 %, and the calculator shows 30.
- The percent button works on phone calculators, basic calculators, and scientific calculators.
- If your calculator has no percent button, multiply and then divide by 100 manually — the result is identical.
- You can also convert the percentage to a decimal first (20% = 0.20) and multiply directly, which some people find easier to remember.
Using the percent button on different calculator types
On an iPhone or Android phone, open the calculator app and turn the phone sideways to see the percent button (%). Type the number, press ×, type the percentage, press %, and the answer appears. You do not need to press equals.
On a physical calculator, the percent button looks like a % symbol. The steps are the same: number, multiply, percentage, percent button. If your calculator does not have a percent button, you can still find the answer by dividing by 100 after you multiply.
Scientific calculators also have a percent button in the same location. Some scientific calculators show the percent button in a different color or require you to press a "shift" key first — check your calculator's manual if you cannot find it immediately.
The decimal method: convert the percentage first
Another way to find a percentage is to convert it to a decimal before you multiply. To do this, divide the percentage by 100 first. For example, 20% becomes 0.20. Then multiply the number by the decimal: 150 × 0.20 = 30.
This method gives the same answer as the percent button, but it takes one extra step. Some people find it easier to understand because you can see the decimal conversion happen. Others prefer the percent button because it is faster.
Both methods are correct. Choose whichever one feels more natural to you, or use the percent button if your calculator has one — it is the quickest route.
Finding what percentage one number is of another
Sometimes you need to work backwards: you know two numbers and want to find what percentage one is of the other. For example, if you scored 45 points out of 60 on a test, what percentage is that?
Divide the first number by the second, then multiply by 100. Type 45 ÷ 60 × 100, and the calculator shows 75. That means 45 is 75% of 60. If your calculator has a percent button, you can press it instead of multiplying by 100, and the answer appears the same way.
This is the reverse of the first method. Instead of starting with the whole number and finding a piece of it, you start with the piece and find what percentage it represents.
Checking your answer with a real-world example
Let's say you are buying something that costs $80 and it is on sale for 25% off. To find the discount amount, multiply 80 × 25 %, and the calculator shows 20. That means the discount is $20, so you pay $80 − $20 = $60.
To check: is $20 actually 25% of $80? Divide 20 ÷ 80 × 100, and you get 25. Yes, it matches. This backwards check works for any percentage problem and helps you catch mistakes before you finish.
Real-world percentages come up in sales, tips, test scores, interest rates, and tax calculations. Once you know how to use the calculator, the method is the same no matter what the percentage represents.
What to do if your calculator does not have a percent button
If you have an older calculator or a very basic model without a percent button, you can still find any percentage by doing the math in two steps. Multiply the number by the percentage, then press equals. Write down the answer. Then divide that answer by 100 and press equals again.
For example, to find 20% of 150 without a percent button: type 150 × 20 =, which gives 3000. Then type 3000 ÷ 100 =, which gives 30. The final answer is 30, the same as if you had used the percent button.
This method is slightly longer, but it works on any calculator that has multiply and divide buttons. Most people find the percent button faster once they know it exists, but the manual method is reliable if you do not have one.
Frequently Asked Questions
Why do I divide by 100 to find a percentage?
Percent means "per hundred," so 20% literally means 20 out of every 100. When you multiply 150 × 20, you get 3000, which is 20 times the whole number. Dividing by 100 scales it back down to the right size: 3000 ÷ 100 = 30, which is the correct 20% of 150.
Is the percent button the same on all calculators?
The percent button works the same way on most calculators, but some older or specialty models may behave differently. If you press the percent button and get an unexpected answer, check your calculator's manual or try the divide-by-100 method instead, which always works.
Can I find a percentage on a calculator without a display?
No, you need to see the numbers to know when to stop and what the answer is. If your calculator has no display screen, you cannot use it to find a percentage. A phone calculator or a basic calculator with a display will work.
What if I need to find a percentage of a percentage?
Multiply the number by the first percentage, then multiply that answer by the second percentage, then divide by 10,000. For example, to find 20% of 50% of 200: type 200 × 20 × 50 ÷ 10,000 =, which gives 20. You divide by 10,000 because you are multiplying two percentages together (100 × 100).