The basic percent button method

Most calculators have a percent button marked with the % symbol. To find a percentage of a number, enter the number first, then press %, then enter the percentage you want. For example, to find 20% of 50, you would type: 50, then %, then 20. The calculator shows you 10 (which is 20% of 50).

The order matters here. You start with the base number, not the percentage. If you reverse it and type 20 % 50, you will get a different answer that is not what you need. The percent button works by taking whatever number you entered first and multiplying it by the percentage you enter second, then dividing by 100 automatically.

This method works on nearly every calculator — phone calculators, basic four-function calculators, and scientific calculators all have this button in the same place. If your calculator does not have a visible % button, check whether it is a second function (usually accessed by pressing Shift or a colored button first).

Key Takeaways

  • Enter the base number first, press %, then enter the percentage to find what that percentage equals.
  • To add or subtract a percentage from a number, enter the base number, press +, then the percentage, then =.
  • If your calculator has no % button, you can multiply the number by the decimal form of the percentage instead (20% = 0.20).
  • The percent button saves time and reduces mistakes compared to doing the math by hand or converting percentages to decimals yourself.

Adding or subtracting a percentage from a price

When you need to add a percentage to a number (like calculating tax or a tip), use the plus button with the percent button. Type the base number, press +, enter the percentage, then press =. For example, to add 15% tip to a $40 bill, type: 40, +, 15, %, =. The answer is 46, which is $40 plus $6 (the 15% tip).

Subtracting a percentage works the same way but with the minus button. If something is 25% off and the original price is $80, type: 80, −, 25, %, =. The calculator shows 60, which is the sale price. This is faster and more accurate than calculating the discount separately and then subtracting it.

The reason this works is that the calculator understands you want to find the percentage of the original number, then add or subtract it. You do not have to figure out what 15% of $40 is on your own — the calculator does that step for you.

Using decimals if your calculator has no percent button

If your calculator does not have a percent button, you can still find percentages by converting them to decimals first. To convert a percentage to a decimal, divide it by 100 or move the decimal point two places to the left. So 20% becomes 0.20, 15% becomes 0.15, and 5% becomes 0.05.

Once you have the decimal, multiply it by the base number. To find 20% of 50 without a percent button, type: 50 × 0.20 = 10. To add 15% to $40, type: 40 × 0.15 = 6, then add 6 to 40 to get 46. This takes one extra step compared to using the percent button, but the answer is the same.

This method also works on any calculator, including very old or very basic ones. If you are using a phone calculator and cannot find the % button, try rotating your phone to landscape mode — many phone calculators hide the percent button until you switch the view.

Finding what percentage one number is of another

Sometimes you need to know what percentage one number represents of a total. For example, if you scored 85 points out of 100, what percentage is that? Divide the first number by the second, then press the percent button. Type: 85 ÷ 100, then %. The answer is 85 (meaning 85%).

This works because dividing gives you the decimal form of the percentage (0.85), and pressing % converts it to the percentage form (85%). You can use this method for any comparison — if you spent $30 out of a $150 budget, type 30 ÷ 150, then %, and the calculator shows 20 (meaning you spent 20% of your budget).

If your calculator does not have a percent button, just stop after the division. 85 ÷ 100 = 0.85, which you can read as 85%. Multiply by 100 in your head if you want the percentage number, but the decimal form tells you the same thing.

Common mistakes to avoid

The most common mistake is pressing the buttons in the wrong order. Remember: base number first, then the operation, then the percentage. If you type the percentage first, you will get a nonsense answer. Your calculator cannot know what you are taking a percentage of unless you tell it the base number first.

Another mistake is forgetting to press = at the end. Some calculators show a preview of the answer as you type, which can trick you into thinking you are done. Always press = to confirm the final answer, especially when adding or subtracting percentages.

A third mistake is confusing the decimal method with the percent button method. If you use the percent button, do not also multiply by 0.01 or divide by 100 — the button does that for you. If you do both, you will get an answer that is 100 times too small.

Percentages on phone calculators

Phone calculators work the same way as physical calculators, but the layout is sometimes different. On an iPhone, open the Calculator app and make sure you are in Standard view (not Scientific). The % button is in the second row on the right side. On Android, the location varies by phone, but the % button is usually visible in the main calculator view.

If you cannot find the % button on your phone, try rotating your phone to landscape mode. Many phone calculators expand to show more buttons when you turn the screen sideways, and the percent button often appears only in landscape view. You can also search your phone's app store for "calculator" to download a different calculator app if the built-in one does not have the features you need.

Phone calculators sometimes behave slightly differently than physical calculators, especially with the order of operations. If you get an unexpected answer, try entering the numbers in a different order or using the decimal method instead. The decimal method always works the same way on every device.

Frequently Asked Questions

What if I want to find the percentage increase or decrease between two numbers?

Subtract the smaller number from the larger number, then divide by the original number, then press %. For example, if a price went from $50 to $65, type: 65 − 50 = 15, then 15 ÷ 50, then %. The answer is 30, meaning a 30% increase. This method works for any comparison where you want to know how much something changed as a percentage.

Can I use the percent button to find the percentage of a percentage?

Yes, but you have to do it in steps. To find 20% of 50%, first find 20% of 50 (which is 10), then find what percentage 10 is of 50 (which is 20%). In most real situations, you would not need to do this, but the calculator can handle it if you break it into smaller pieces.

Why does my calculator show a different answer when I use the percent button versus the decimal method?

This usually means you entered the numbers in a different order or pressed a different button. Double-check that you typed the base number first, then the operation, then the percentage. Both methods should give the same answer if you enter the numbers in the same order. If they still differ, your calculator may have a quirk — try the decimal method, which works consistently on all devices.

Do I need a special calculator to work with percentages?

No. Any calculator with a percent button will work, and even a basic four-function calculator (with only +, −, ×, ÷) can handle percentages if you use the decimal method. You do not need a scientific or graphing calculator unless you are doing more advanced math.