How to Put Percent in Calculator

This guide shows you how to enter percentages on a standard calculator, a scientific calculator, or a phone calculator app. You’ll learn the correct keystrokes for finding a percent of a number, adding or subtracting a percent, and converting between percents and decimals. No special knowledge is needed—just a calculator and a few examples to follow.

Formula

To find P% of N, use the formula:

Result = (P / 100) × N

• P = the percentage (e.g., 15 for 15%)
• N = the number you want the percentage of
• Result = the value that represents P% of N

For example, 15% of 200 = (15 / 100) × 200 = 0.15 × 200 = 30.

Worked Example

Using the default values from the calculator above (15% and 200):

1. Convert 15% to a decimal: 15 ÷ 100 = 0.15
2. Multiply by 200: 0.15 × 200 = 30

The calculator gives 30, which matches.

Step-by-Step: How to Put Percent in Calculator

Here are the common ways to enter a percentage, depending on what you want to do.

1. Finding a Percentage of a Number (e.g., 15% of 200)

1. Turn on your calculator.
2. Enter the percentage number: 15.
3. Press the % key (if available). On most basic calculators, this converts 15 to 0.15 automatically.
4. Press the multiplication key ×.
5. Enter the number: 200.
6. Press the equals key =.
7. The display shows 30.

If your calculator does not have a % key, do this instead:

1. Enter 15.
2. Press ÷.
3. Enter 100.
4. Press = (you get 0.15).
5. Press ×.
6. Enter 200.
7. Press = (you get 30).

2. Adding a Percentage (e.g., Add 15% to 200)

This is common for tips, tax, or markup. To add 15% to 200:

1. Enter 200.
2. Press +.
3. Enter 15.
4. Press % (the calculator may show 30, which is 15% of 200).
5. Press = (you get 230).

If no % key, multiply 200 by 0.15 to get 30, then add 200 to get 230.

3. Subtracting a Percentage (e.g., Subtract 15% from 200)

1. Enter 200.
2. Press − (minus).
3. Enter 15.
4. Press % (shows 30).
5. Press = (you get 170).

4. Converting a Percent to a Decimal

1. Enter the percentage (e.g., 25).
2. Press ÷.
3. Enter 100.
4. Press = (you get 0.25).

5. Converting a Decimal to a Percent

1. Enter the decimal (e.g., 0.75).
2. Press ×.
3. Enter 100.
4. Press = (you get 75).

Common Mistakes

• Forgetting to divide by 100 when there is no % key. Entering 15 × 200 gives 3000, not 30.
• Using the % key incorrectly on scientific calculators. Some require you to press Shift or 2nd to access the % function.
• Mixing up order of operations when adding a percentage. For example, on some calculators, 200 + 15% might give 230, but on others you must press = after the % to see the result.
• Rounding too early when doing multi-step calculations. Keep extra decimal places until the final step.

Tips

• If your calculator has a % key, test it with a simple example (like 10% of 50) to see how it behaves.
• For phone calculators, you may need to rotate to landscape mode to see the % key.
• When in doubt, convert the percent to a decimal manually (divide by 100) and multiply. This always works.
• Use parentheses on scientific calculators to ensure correct order: (15/100)*200.

Troubleshooting

Problem: The % key gives a weird result.
Try pressing the equals sign after the % key. Some calculators wait for you to confirm the conversion.

Problem: My calculator does not have a % key.
Use the manual method: divide by 100, then multiply. Or multiply by 0.01.

Problem: The result is too large or too small.
Check if you entered the decimal correctly. For example, 15% should be 0.15, not 1.5. If you see 1.5, you likely forgot to divide by 100.

Problem: The calculator shows a fraction or scientific notation.
Press the S↔D or F↔D key to toggle between fraction and decimal display.

Frequently Asked Questions

How do I calculate 20% of 150 on a basic calculator?

Enter 20, press %, press ×, enter 150, press =. You should get 30. If no % key, do 20 ÷ 100 × 150.

What does the % key actually do?

It divides the number by 100, turning a percentage into a decimal. For example, pressing 25% gives 0.25 on most calculators.

How do I add 10% to a price on a calculator?

Enter the price, press +, enter 10, press %, press =. For a $50 item, you get $55.

How do I subtract 10% from a price?

Enter the price, press −, enter 10, press %, press =. For $50, you get $45.

Why does my calculator give 15% of 200 as 30 sometimes and 0.15 other times?

If you press just 15% and then =, some calculators show 0.15 (the decimal). To get the percentage of a number, you must multiply after pressing %. The order matters.

Can I use a percentage in a scientific calculator without a % key?

Yes. Just divide by 100 or multiply by 0.01. For example, to compute 15% of 200, type 15/100*200.

Related

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in p | Percent | % | 15 | 0
in n | Number | - | 200 | 0
out result | Percent of number | - | (p / 100) * n | 2