The Basic Percentage Formula in Excel

To calculate a percentage in Excel, divide the part by the whole, then multiply by 100. The formula is =(part/whole)*100. For example, if you want to find what percentage 25 is of 200, you would enter =25/200*100 in a cell, and Excel returns 12.5.

You can also skip the multiplication by 100 and format the cell as a percentage instead — Excel will display the decimal as a percentage automatically. So =25/200 formatted as percentage also shows 12.5%. This second method is cleaner because the cell still holds the decimal value, which is useful if you need to use that number in other calculations.

The most common mistake is forgetting to use parentheses. If you type =part/whole*100 without parentheses around the division, Excel follows order of operations and may calculate it wrong. Always wrap the division in parentheses: =(part/whole)*100.

Key Takeaways

  • The percentage formula is =(part/whole)*100, or you can use =(part/whole) and format the cell as percentage.
  • Use parentheses around the division to make sure Excel calculates it in the right order.
  • You can reference cell addresses instead of typing numbers, so =(A1/B1)*100 calculates the percentage of whatever is in cells A1 and B1.
  • To find what a percentage of a number is (like 15% of 200), use =(percentage/100)*whole, which gives 30.
  • Copy a formula down a column to calculate percentages for multiple rows at once by dragging the fill handle.

Using Cell References Instead of Numbers

In real spreadsheets, you rarely type raw numbers into a formula. Instead, you reference the cells that hold those numbers. If your part is in cell A2 and your whole is in cell B2, the formula becomes =(A2/B2)*100.

This approach is powerful because you can copy the formula down to other rows and Excel automatically adjusts the cell references. If you copy =(A2/B2)*100 down to row 3, it becomes =(A3/B3)*100 without you having to retype anything. Click the cell with your formula, grab the small square at the bottom right corner (called the fill handle), and drag it down as far as you need.

Calculating What Percentage One Number Is of Another

This is the most common task: you have two numbers and want to know what percentage the first is of the second. If sales were 450 last month and 600 this month, what percentage increase is that?

Put 450 in cell A1 and 600 in cell B1. In cell C1, enter =(B1-A1)/A1*100. This subtracts the old value from the new value, divides by the old value, and multiplies by 100. The result is 33.33, meaning a 33.33% increase. The formula works the same way for decreases — if the new number is smaller, the result will be negative, showing a percentage drop.

Finding a Percentage of a Number

Sometimes you need to work backwards: you know the percentage and the whole, and you want to find the part. For example, what is 20% of 150?

The formula is =(percentage/100)*whole. So =(20/100)*150 returns 30. If the percentage is already in a cell (say A1 holds 20 and B1 holds 150), use =(A1/100)*B1. This is useful for calculating discounts, tax amounts, or commission.

Formatting Cells as Percentage

After you enter a formula like =A1/B1, the cell shows a decimal: 0.25. To display it as a percentage (25%), select the cell and format it. In Excel, right-click the cell and choose Format Cells, then select Percentage from the Category list. In Google Sheets, click the percentage button (%) in the toolbar.

When you format as percentage, Excel multiplies the displayed value by 100 automatically — so the cell still holds 0.25 internally, but shows 25%. This matters if you use that cell in another formula, because Excel uses the decimal value, not the displayed percentage. If you want to see two decimal places (25.00%), right-click again, choose Format Cells, and set the decimal places to 2.

Common Percentage Calculations in Spreadsheets

A few scenarios come up repeatedly. To calculate a percentage increase or decrease, use =((new-old)/old)*100. To find what percentage of a total one item represents, use =(item/total)*100 — useful for budget breakdowns or sales by region. To explore a percentage discount, use =price*(1-discount%/100), so a 15% discount on $100 is =100*(1-15/100), which gives $85.

For tax calculations, if the tax rate is 8% and the price is $50, the tax amount is =50*0.08 and the total is =50+(50*0.08) or straightforward =50*1.08. These formulas work the same way whether you type the percentage as a decimal (0.08) or use a cell reference (if B1 holds 8, use =50*(B1/100)).

Avoiding Errors When Dividing by Zero

If your formula divides by a cell that is empty or contains zero, Excel shows #DIV/0! error. This happens often when you copy a formula down a column and some rows have missing data.

To prevent this, wrap your formula in an IF statement: =IF(B1=0,"",A1/B1*100). This says: if B1 is zero, leave the cell blank; otherwise, calculate the percentage. You can also use IFERROR: =IFERROR(A1/B1*100,""), which returns blank if any error occurs. These approaches keep your spreadsheet clean and readable.

Frequently Asked Questions

Do I need to multiply by 100 if I format the cell as percentage?

No. If you use =A1/B1 and format the cell as percentage, Excel displays it as a percentage automatically. If you use =(A1/B1)*100 and format as percentage, Excel multiplies by 100 again, showing 2500% instead of 25%. Use one method or the other, not both.

How do I calculate percentage change between two numbers?

Use =((new-old)/old)*100. If old is in A1 and new is in B1, enter =((B1-A1)/A1)*100. A positive result is an increase; a negative result is a decrease.

Can I use percentage formulas in Google Sheets the same way as Excel?

Yes. The formulas are identical. The only difference is the formatting button — Google Sheets has a percentage (%) button in the toolbar instead of a right-click menu. The underlying math works the same way.

What if I want to show percentages with no decimal places?

Right-click the cell, choose Format Cells, select Percentage, and set decimal places to 0. In Google Sheets, format as percentage, then click the decrease decimal button in the toolbar until it shows zero decimals.

How do I calculate what percentage of my budget each expense is?

Put each expense in column A and the total budget in a cell (say D1). In column B, enter =A1/$D$1*100 for the first expense. The dollar signs lock the total budget cell so it does not change when you copy the formula down. Each row then shows what percentage that expense is of the total.