The basic percentage 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 enter: 50, then %, then 20. The calculator shows 10.

This works because the % button tells the calculator to multiply the first number by the second number divided by 100. You do not need to think about that part — the button does it for you. The result appears on your screen right away.

The order matters. If you enter 20 first and then 50, you will get the wrong answer. Always start with the total amount you are taking a percentage of.

Key Takeaways

  • The % button on your calculator multiplies the first number by the percentage divided by 100, so you enter the total first, then %, then the percentage amount.
  • To add a percentage to a number (like calculating a tip or sales tax), enter the total, then +, then the percentage, then = to see the new amount.
  • To subtract a percentage (like a discount), enter the total, then −, then the percentage, then = to see what remains.
  • If your calculator does not have a % button, you can divide by 100 and multiply by hand: 50 ÷ 100 × 20 gives you 20% of 50.

Adding a percentage to a number

When you need to add a percentage — such as calculating a tip on a restaurant bill or adding sales tax to a purchase — the process is slightly different. Enter the original amount, then press +, then enter the percentage, then press the % button, then press =.

For example, if your restaurant bill is $45 and you want to add a 18% tip, enter: 45, then +, then 18, then %, then =. The calculator shows 53.10, which is your bill plus the tip. You are not calculating 18% of $45 in isolation — you are adding that amount to the original $45.

This method works on most standard calculators. Some older or simpler models may not support this sequence, in which case you would need to calculate the percentage separately and add it by hand.

Subtracting a percentage from a number

Discounts and markdowns use the same logic as adding, but in reverse. Enter the original price, then press −, then enter the percentage, then press %, then press =.

If an item costs $80 and is on sale for 25% off, enter: 80, then −, then 25, then %, then =. The calculator shows 60, which is the sale price. The calculator subtracted 25% of $80 (which is $20) from the original $80.

This is useful for comparing prices when shopping or figuring out what you will actually pay after a discount is applied.

Calculating what percentage one number is of another

Sometimes you know two numbers and need to find what percentage one is of the other. For instance, if you scored 42 points out of 50 on a test, what percentage is that?

Divide the first number by the second, then press the % button. Enter: 42, then ÷, then 50, then %. The calculator shows 84, meaning 42 is 84% of 50. Some calculators will show this as 0.84 and you multiply by 100 in your head, but most modern calculators handle the conversion automatically.

This method works for any comparison: sales figures against targets, completed tasks against total tasks, or actual spending against a budget.

When your calculator has no percent button

Older calculators or very basic models sometimes lack a % button. You can still calculate percentages by hand using division and multiplication.

To find a percentage of a number, divide the number by 100, then multiply by the percentage. For 20% of 50: enter 50, then ÷, then 100, then ×, then 20, then =. You get 10. This is slower than using the % button, but it produces the same result.

To add or subtract a percentage without a % button, calculate the percentage amount first using the division method above, then add or subtract it from the original number in a separate step.

Common mistakes and how to avoid them

The most frequent error is entering the numbers in the wrong order. Remember: the total or base number always comes first. If you are finding 15% of 200, you enter 200 first, not 15.

Another common mistake is pressing = too early. When you are adding or subtracting a percentage, you must press the % button before pressing =. If you press = right after entering the percentage number, the calculator will not know you meant a percentage and will give you the wrong answer.

If your answer seems too large or too small, check whether you entered the numbers in the right order and pressed % before =. Recalculating takes only a few seconds and catches most errors when ready.

Frequently Asked Questions

What if my calculator shows a decimal instead of a whole number for the percentage?

Some calculators display percentages as decimals — for example, 0.20 instead of 20. Both are correct; 0.20 and 20% mean the same thing. If you see a decimal and want to see it as a percentage, multiply by 100 in your head or on paper. A decimal of 0.84 is the same as 84%.

Can I calculate a percentage of a percentage on a calculator?

Yes. Calculate the first percentage, then use that result to calculate the second percentage. For example, to find 10% of 20% of 500, first find 20% of 500 (which is 100), then find 10% of 100 (which is 10). You perform two separate calculations in sequence.

Why do I get different answers when I calculate a discount different ways?

You should not, if you are using the same numbers. Double-check that you entered the original price first, then the discount percentage, and pressed % before =. If you calculated the discount amount separately and subtracted it by hand, make sure you subtracted from the original price, not from something else.

Does the order of operations matter when adding multiple percentages?

Yes, if the percentages are applied to different base amounts. If you are adding two separate percentages to the same number, calculate each one independently and add the results. If one percentage is applied to the result of another, calculate the first percentage, then use that new total as the base for the second percentage.