Percentage Formula in Excel: 5 Everyday Calculations

The right percentage formula in Excel depends on the question you are asking. "What is 15% of 80?" needs a different formula from "What percent of the target did we hit?" or "How much did sales grow?". This guide covers the five calculations people use every day, each with one short formula and a worked example. It is for beginners, office workers and anyone with an Excel test coming up.

How Excel stores percentages#

Excel stores a percentage as a decimal. 15% is stored as 0.15, and 100% is 1. The percent sign is only a display format.

That has three useful effects:

• =80*15% and =80*0.15 both return 12.
• You never multiply by 100. Leave the result as a decimal and apply the % format.
• If a cell holds 15 and you apply the percent format, it shows 1500%. Type 15% or 0.15 instead.

To apply the format, select the cells and press Ctrl+Shift+% on Windows or Control+Shift+% on a Mac. It shows whole percentages; click Increase Decimal on the Home tab for more digits. The guide to formatting numbers as currency and percent has the other number shortcuts.

The five percentage formulas at a glance#

In real sheets, use cell references instead of typed numbers, so the answers update when the data changes. Each formula is explained below.

1. How to calculate a percentage of a number#

Multiply the number by the percentage. With a price of 80 in B2 and a 15% tip rate in C2:

=B2*C2

The result is 12. This is how you work out a commission, a tax amount, a tip or a deposit. To use one rate for a whole column, put it in a single cell and lock it with $, like =B2*$F$1.

2. How to find what percent one number is of another#

Divide the part by the whole. In this page's exercise, Ana's target is 8,000 in B2 and her actual sales are 9,200 in C2:

=C2/B2

The result is 1.15, which shows as 115% with the percent format. She beat her target by 15%. Ben's 4,500 against 6,000 gives 75%, and Chen's 7,500 against 7,500 gives exactly 100%.

When the whole is a column total, such as each region's share of all sales, lock the total cell with $. That case has its own guide: how to calculate percentage of total in Excel.

3. How to calculate percent change#

Subtract the old value from the new one, then divide by the old value. With last month's 200 orders in B2 and this month's 250 in C2:

=(C2-B2)/B2

The result is 25%. A negative result means a fall: from 250 down to 200 is -20%, not -25%, because you always divide by the starting value. The brackets matter, since Excel divides before it subtracts. The full guide is the percent change formula in Excel, and for growth over several years, use the CAGR formula.

4. How to increase or decrease a number by a percentage#

Multiply by 1 plus the percentage to increase, or 1 minus the percentage to decrease. With 80 in B2 and 15% in C2:

=B2*(1+C2)

The result is 92. For a 15% decrease, =B2*(1-C2) gives 68. This one formula covers price rises, pay rises, markups and discounts. See how to increase a number by a percentage for rounding and whole-column examples, and how to calculate a discount in Excel for sale prices.

5. How to find the original number before a percentage#

To undo a percentage that was added, divide by 1 plus the percentage. If a price including 20% tax is 120 in B2 and the rate is in C2:

=B2/(1+C2)

The result is 100, the price before tax. A common mistake is to subtract 20% instead: =B2*(1-C2) gives 96, which is wrong, because the 20% was calculated on 100, not on 120.

How to use a percentage stored in a cell#

Real sheets keep rates in cells, not inside formulas, so you can change them in one place. Type the rate with its percent sign, like 15%, and Excel stores 0.15 and formats the cell for you. If the cell is already formatted as a percentage, typing 15 also gives 15%.

When many rows use the same rate, lock it with $ signs before filling down. With a 12% commission rate in F1 and sales in column B, =B2*$F$1 works in every row. A sale of 2,500 earns 300. Press F4 while editing to add the signs (fn+F4 or ⌘T on a Mac).

Common percentage mistakes#

Most wrong percentages come from one of these:

• Multiplying by 100 and then applying the % format, which shows 7500%.
• Dividing by the wrong number in a percent change. Divide by the old value.
• Missing brackets: =C2-B2/B2 divides first and gives nonsense.
• #DIV/0! when the whole or the old value is 0 or blank. Wrap the formula in IFERROR: =IFERROR(C2/B2,"").
• Percent vs percentage points: going from 30% to 33% is a rise of 3 percentage points, but a 10% increase.

Practise it#

Percentages appear in almost every Excel test, usually as percent change or part of a whole. Practise percentages and percent change in a live spreadsheet: you type the formula, it checks it instantly, and you format the result as a percentage. If formulas are still new, start with your first formulas. Try the target exercise on this page first.