Google Sheets: Get a Percentage of a Number

To get a percentage of a number in Google Sheets, multiply the number by the percentage: if A1 contains 150 and B1 contains 20%, enter =A1*B1 in C1. The result is 30. The key is to enter the percentage as a percentage, such as 20%, rather than as the whole number 20.

The Basic Percentage Calculation

A percentage means a portion of 100. For example, 20% is equivalent to 20 out of 100, or 0.2. Multiplication converts that rate into an amount: 20% of 150 is 0.2 × 150, which equals 30. In Sheets, you can use cell references so the result updates whenever you change the number or the rate.

With the original number in A1 and the rate in B1, enter =A1*B1 in C1; if A1 is 150 and B1 is 20%, C1 returns 30. You can also type the values directly into a formula: with no particular cell layout assumed, =150*20% returns 30. A formula using cell references is usually easier to maintain because you can change the inputs without editing the formula.

To set up the cell-based example:

Enter 150 in A1.
Enter 20% in B1. You can type the percent sign as part of the value.
Enter =A1*B1 in C1 and press Enter.
Check that the result is 30. If the result cell is set to a currency format, it may instead appear as a currency amount, depending on that cell’s formatting.

Enter and Format the Percentage Correctly

Google Sheets stores a percentage as a decimal value. A cell displaying 20% has the underlying value 0.2, so multiplying by that cell gives the intended portion. You can type 20% directly, or type 0.2 and apply percentage formatting. Both represent the same rate for calculations.

To display a value as a percentage, select the cell or range, then choose Format > Number > Percent. The toolbar also has a format-as-percent button. Applying this format changes how the value is displayed; it does not turn an arbitrary whole number into the percentage you may have intended. If you enter 20 and then format it as a percentage, Sheets displays 2,000%, because 20 is twenty whole units, equal to 2,000 hundredths.

This distinction also matters for the answer cell. If 20% of 150 returns 30, formatting that result as a percentage displays 3,000%, because the numeric result is 30. For a portion-of-a-number calculation, the answer is usually best shown as a regular number, currency, or another format appropriate to the data—not as a percentage. Use percent formatting for the rate, or for a ratio that represents a share of a total.

Calculate What Percentage One Number Is of Another

A related question is how to find what percentage a part represents of a whole. That calculation divides the part by the whole, rather than multiplying the whole by a percentage. For example, if 30 is a part of a total of 150, the share is 0.2, which displays as 20% when formatted as a percentage.

With the part in A1 and the total in B1, enter =A1/B1 in C1; if A1 is 30 and B1 is 150, the result is 0.2, or 20% after percentage formatting. Choose Format > Number > Percent for C1 if you want it to show the percent sign. Make sure the total is the denominator: reversing the references would answer a different question.

If the whole could be zero, division by zero produces an error. You can avoid an error display by checking the denominator first. With the part in A1 and the whole in B1, enter =IF(B1=0,0,A1/B1) in C1; if B1 is zero, it returns 0, otherwise it returns the part divided by the whole. Format C1 as a percentage if appropriate. Returning zero is only one possible choice; depending on the meaning of your data, you may prefer to leave the result blank or show a note that the percentage cannot be calculated.

Add or Subtract a Percentage

Finding a percentage amount and adjusting a number by a percentage are different operations. Multiplying 150 by 20% gives the amount 30. If you want to increase 150 by 20%, you need the original 150 plus the additional 30, for a total of 180. If you want to reduce 150 by 20%, subtract 30, leaving 120.

With the starting value in A1 and the rate in B1, enter =A1*(1+B1) in C1 to increase the value; for 150 and 20%, the result is 180. With the same cell layout, enter =A1*(1-B1) in C1 to decrease it; the result is 120. These formulas assume B1 contains 20%, not 20. The form using 1 plus or minus the rate is convenient because it returns the adjusted total directly.

For a discount example, suppose A1 contains a price of 80 and B1 contains a discount rate of 15%. With that layout, =A1*B1 returns 12, the discount amount, while =A1*(1-B1) returns 68, the price after the discount. If you need to show both the discount and the final price, use separate result cells and label them clearly.

Apply One Percentage to Many Numbers

If a single percentage applies to a list of values, put the rate in one cell and refer to it from each calculation. For example, assume A2:A5 contains four amounts and B1 contains a rate of 20%. In C2, enter =A2*$B$1, then fill or copy the formula down through C5. The first result uses A2 and the fixed rate in B1; subsequent rows use A3, A4, and A5 while continuing to use B1.

The dollar signs make B1 an absolute reference. Without them, copying =A2*B1 down one row changes the reference to B2, which is usually not wanted when the rate is stored in a single cell. You can drag the small square at the lower-right corner of the selected formula cell down the column, or copy and paste the formula into the required cells.

For a longer sheet, labels help prevent mistakes. Use headings such as Amount, Rate, and Percentage amount, and keep input cells visually distinct if that suits your workflow. If the rate changes later, update the single rate cell and the calculated amounts update automatically. Before filling formulas down, check that the first result is correct and that the rate reference has dollar signs.

Common Errors and How to Fix Them

The answer is 100 times too large: A rate may have been entered as 20 instead of 20%. Enter 20% or 0.2 for a twenty-percent rate. A cell displaying 2,000% generally contains 20 rather than 0.2.
The result displays with a percent sign: The result cell may be formatted as a percentage. Change it to Format > Number > Number, Currency, or an appropriate format. The underlying calculation may already be correct.
The answer is blank or unexpected: Check that the referenced cells contain numeric values. A value that looks like a number but is stored as text may not behave as expected in arithmetic.
Copied formulas use the wrong rate cell: Make the rate reference absolute, as in =A2*$B$1, before filling the formula down.
The percentage calculation returns an error: For a part divided by a whole, confirm that the whole is not zero and that the references are in the intended order.

It is also useful to distinguish rounding in appearance from rounding in the calculation. A result can be stored with more decimal places than the cell shows. For example, a currency-formatted cell may display two decimal places while retaining additional precision. Increasing the displayed decimal places can help you inspect the value. Do not round a result just because the display is rounded unless your task specifically requires rounding the stored calculation.

Which Formula Should You Choose?

Choose the operation based on the question you are answering. The same word, percentage, can refer to the rate, the amount represented by the rate, or a share of a total. Those are related but distinct calculations.

How much is 20% of 150? Multiply the number by the rate: =150*20%, which returns 30.
30 is what percent of 150? Divide the part by the total: =30/150, which returns 0.2; format the result as a percentage to display 20%.
What is 150 after a 20% increase? Multiply by one plus the rate: =150*(1+20%), which returns 180.
What is 150 after a 20% decrease? Multiply by one minus the rate: =150*(1-20%), which returns 120.

Each direct-value formula above assumes the numbers are entered exactly as shown in the formula, so it does not depend on a cell layout. For a working sheet, replace those fixed numbers with references to the cells that contain your inputs. The formulas use ordinary multiplication and division, so the basic calculation works in Google Sheets and Excel. The menu wording and interface can differ between the programs, but the arithmetic does not.

Frequently Asked Questions

How do I calculate 10% of a number in Google Sheets?
Multiply the number by 10%. With the number in A1, enter =A1*10% in another cell. If A1 contains 250, the result is 25. You can also place 10% in a separate rate cell and multiply by that cell.

Should I type 20 or 20% in the percentage cell?
Type 20% for a twenty-percent rate. You may also type 0.2 and format the cell as a percentage. Typing 20 and then choosing percentage formatting displays 2,000%, because the stored value is twenty rather than 0.2.

Why does my percentage result show 3,000%?
The result cell is likely formatted as a percentage even though it contains an amount such as 30. Change its format to a number or currency. Percentage formatting is suited to a rate or a part divided by a whole, not generally to the amount produced by multiplying a number by a rate.

How do I calculate a percentage increase in Google Sheets?
Multiply the original value by one plus the rate. With the starting value in A1 and the rate in B1, use =A1*(1+B1). If A1 is 200 and B1 is 5%, the new value is 210. To calculate only the increase amount, use =A1*B1, which returns 10.

Can Google Sheets calculate a percentage automatically when I change the number?
Yes. Use cell references in the formula, such as multiplying the amount cell by the rate cell. Sheets recalculates the result when an input changes. If you copy the formula down a list while keeping one rate fixed, use an absolute reference such as $B$1.

Does the formula work in Excel too?
Yes. Basic multiplication and division formulas such as =A1*B1 and =A1/B1 work in both Google Sheets and Excel. The formulas are the same, although formatting controls and menu paths may not look identical.

Try it: the Date Difference Calculator: days, months, years and weekdays between two dates, with the DATEDIF formulas.

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Sources: Function behaviour and menu paths: Microsoft Support documentation for Excel. Method & sources

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