Excel Formula for Percentage of a Number

To calculate a percentage of a number in Excel, multiply the number by the percentage: if A2 contains 150 and B2 contains 20%, enter =A2*B2 in C2. The result is 30. This works because Excel stores 20% as the decimal value 0.2.

How the percentage formula works

A percentage means a part out of 100. To find 20% of 150, convert 20% to 0.2 and multiply: 150 × 0.2 = 30. Excel performs that conversion when a cell contains a percentage, so the formula can use the cell value directly. Multiplication is the core operation; the main thing to get right is how the percentage is entered.

For a worksheet, you might put the original number in one cell, the rate in a second, and the result in a third. With 150 in A2 and 20% in B2, enter =A2*B2 in C2; C2 returns 30. If you change A2 or B2 later, the result updates automatically. Cell references also make it easy to copy the calculation down a column for many rows.

You can type the calculation directly into a cell too. With no cell references needed, enter =150*20% in a blank cell and Excel returns 30. For a reusable worksheet, references are usually clearer and easier to update than fixed numbers typed into every formula.

Enter the percentage correctly

Excel stores percentages as decimal values: 20% is stored as 0.2, 5% as 0.05, and 125% as 1.25. When you type a value with the percent sign, Excel interprets it as a percentage. For example, with 150 in A2 and 20% entered in B2, =A2*B2 in C2 returns 30.

If B2 contains the number 20 rather than 20%, Excel treats it as twenty, not twenty percent. In that case, with 150 in A2 and the whole-number rate 20 in B2, enter =A2*B2/100 in C2 to get 30. Choose one convention for a worksheet and label it clearly. Mixing values such as 20 and 20% in the same rate column can produce results that are off by a factor of 100.

For a percentage-formatted rate, enter 20% and multiply by the cell.
For a whole-number rate such as 20, divide by 100 in the formula.
For a decimal rate such as 0.2, multiply directly; 0.2 represents 20% even if the cell is not displayed with a percent sign.

Set up a reusable worksheet

A simple layout keeps inputs and results easy to check. Put the amount in column A, the percentage in column B, and the calculated portion in column C. For example, enter 150 in A2 and 20% in B2, then enter =A2*B2 in C2. The returned amount is 30.

Enter a descriptive heading such as Amount in A1, Rate in B1, and Portion in C1.
Enter each amount and its percentage on the same row, beginning in row 2.
In C2, use =A2*B2. With A2 equal to 150 and B2 equal to 20%, the result is 30.
Copy the formula down for other rows. Excel adjusts relative references, so the next row uses A3 and B3.

In Microsoft Excel for Microsoft 365 on Windows, copying the formula can be done by dragging the fill handle at the lower-right corner of C2 down the column, or by copying and pasting the cell. On Mac and Excel for the web, the same formula and fill-handle approach work; the interface may look slightly different. If you want a fixed reference to a rate stored in one cell, use an absolute reference such as =A2*$B$1. With the amount in A2 and a fixed percentage in B1, this returns the amount multiplied by the rate in B1. The dollar signs keep B1 fixed when you copy the formula.

Format the result and rate

Formatting changes how a value appears, not the underlying calculation. If C2 returns 30, you can display it as 30, $30.00, or another suitable number format without changing its value. To show a cell as a percentage, select it and choose Home > Number > Percent Style. On Windows, you can also use the Number group’s percentage button on the Home tab. The Mac ribbon offers the corresponding number-format controls.

Apply percentage formatting to the rate, not automatically to the portion. For example, if A2 contains 150 and B2 contains 20%, the formula =A2*B2 in C2 returns 30. If C2 is mistakenly formatted as a percentage, Excel may display the result as 3000%, because the underlying number 30 is being shown as a percentage. Format C2 as a number, currency, or another format that suits the result.

When a percentage display has too many or too few decimal places, use the increase or decrease decimal controls in the Home tab’s Number group. These controls alter the displayed precision, not the stored value. For example, 12.345% might display as 12.35% while the cell retains its more precise value for calculations.

Worked examples for everyday calculations

The same multiplication method applies to prices, scores, budgets, and other quantities. In each case, identify the base number and the rate, then multiply them. Make sure the rate is genuinely entered as a percentage or decimal rather than as a whole number by mistake.

Tax or a fee: With a pre-tax amount of 80 in A2 and a rate of 5% in B2, enter =A2*B2 in C2. The tax amount is 4. This calculates the amount of tax, not the final total.
Discount amount: With an original price of 60 in A2 and a discount rate of 15% in B2, enter =A2*B2 in C2. The discount is 9. The price after discount is 51.
Test score points: With 40 possible points in A2 and a weighting of 25% in B2, =A2*B2 in C2 returns 10 weighted points.
Share of a total: With a category amount of 120 in A2 and a total of 600 in B2, enter =A2/B2 in C2. The result is 0.2; format C2 as a percentage to display 20%.

These examples involve related but distinct questions. Multiplying an amount by a rate finds the portion. Dividing a portion by a total finds what percentage the portion represents. A clear heading helps prevent those two calculations from being confused.

Find the original number from a percentage

Sometimes you know the portion and the rate but need to work backward to find the original amount. Divide the portion by the rate. With a known portion of 30 in A2 and a rate of 20% in B2, enter =A2/B2 in C2; the original amount is 150. This works because 30 divided by 0.2 equals 150.

This reverse calculation depends on the rate being entered as 20%, not the whole number 20. If B2 contains 20, the formula would divide by 20 and return 1.5, which is not the intended answer. Confirm the rate’s displayed value and number format before relying on the result, especially when the worksheet was prepared by someone else.

Percentage of a number versus percentage change

Finding a percentage of a number is not the same as calculating how much a value changed in percentage terms. For a percentage of a number, multiply the base by the rate. For percentage change, subtract the old value from the new value and divide by the old value.

With an old value of 80 in A2 and a new value of 100 in B2, enter =(B2-A2)/A2 in C2. The result is 0.25, or 25% when C2 is formatted as a percentage. The increase is 20 units, and 20 is 25% of the original 80. If the value falls from 100 to 80, the same formula returns -20%, indicating a decrease. A positive or negative result communicates the direction of change.

To add a percentage to an amount, multiply by one plus the rate. With 100 in A2 and 8% in B2, enter =A2*(1+B2) in C2; the result is 108. To subtract a discount, use one minus the rate: with the same inputs, =A2*(1-B2) returns 92. These formulas calculate the final amount, unlike =A2*B2, which calculates only the increase or discount portion. For a real bill, loan, or other financial calculation, confirm the applicable terms and rates with the provider or a qualified professional; these examples are illustrative arithmetic, not financial advice.

Common errors and how to fix them

A result that is unexpectedly large or small often points to a mismatch between the rate’s value and how the formula treats it. Check the cell contents and formatting, then verify the arithmetic with a simple example. Number formatting alone cannot convert an entered whole number into the intended percentage for the calculation.

The answer is 100 times too large: A rate may have been entered as 20 instead of 20%. Enter 20% or divide the whole-number rate by 100 in the formula.
The answer appears as a huge percentage: The result cell may be formatted as Percent Style even though it contains a portion such as 30. Change the result cell to Number or Currency.
The formula shows as text: The cell may be formatted as Text, or the entry may begin with an apostrophe. Change the cell to General or Number, then re-enter the formula.
The result is zero: Check that the rate is not blank or zero and that the amount and rate cells contain numbers rather than text.
The formula does not update as expected: Confirm that it refers to the intended cells and that calculation is not set to manual. In Excel, calculation options are under Formulas > Calculation Options.

For an error-prone workbook, use labels and consistent number formats, and test the formula with inputs whose answer is easy to verify. A small check such as 10% of 100 equaling 10 can reveal a misplaced reference or an incorrectly entered rate quickly.

Frequently Asked Questions

What is the Excel formula for 20% of a number?
Multiply the number by 20%. With the number in A2 and 20% in B2, enter =A2*B2 in C2. If A2 is 150, the result is 30.

How do I calculate a percentage of a total in Excel?
Divide the part by the total. With the part in A2 and the total in B2, enter =A2/B2 in C2, then format C2 as a percentage. For 120 out of 600, the result is 20%.

Do I type 20 or 20% in Excel?
Prefer 20% when you mean twenty percent; Excel stores it as 0.2. If you enter 20 as a whole number, a formula that uses it as a percentage must divide it by 100.

How do I add 10% to a number in Excel?
With the amount in A2 and 10% in B2, use =A2*(1+B2) in C2. For an amount of 200, the result is 220.

How do I subtract a percentage from a number?
With the amount in A2 and the discount rate in B2, use =A2*(1-B2) in C2. If A2 is 200 and B2 is 10%, the result is 180. To calculate just the discount amount, use =A2*B2, which returns 20.

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

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