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How to Calculate Percentages in Excel and Google Sheets

The formulas for percent of a total, percentage change, adding or removing a percentage, and percentage of a column total in Excel and Google Sheets, with the formatting traps that cause wrong answers.

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In Excel and Google Sheets, a percentage is just a decimal shown with a % format: 25% is stored as 0.25. To find what percent A2 is of B2, use =A2/B2 and format the cell as a percentage. For the change from A2 to B2, use =(B2-A2)/A2. To add 15% to A2, use =A2*(1+15%).

Almost every percentage mistake in a spreadsheet comes from one thing: forgetting that the % format multiplies what you see by 100 without changing what is stored. Once that clicks, every formula below is ordinary arithmetic. All of them work identically in Excel and Google Sheets.

How spreadsheets store percentages

Type 25% into a cell and the cell holds 0.25, displayed as 25%. Type 25 into a cell and then apply the % format, and it shows 2500%, because 25 really is 2,500%. So:

  • Enter percentages with the % sign (25%), or as decimals (0.25) and then format.
  • Do not multiply by 100 in a formula and then apply the % format — you will get answers 100 times too big.
  • In formulas, 15% and 0.15 are interchangeable. =A2*15% works.

The six formulas you will actually use

1. What percent is one number of another?

=A2/B2, formatted as %.

With 45 in A2 and 60 in B2, the result is 0.75, displayed as 75%. If you would rather see the number 75 without a % format, use =A2/B2*100 and leave the cell as a plain number — but do not do both.

2. X% of a number

=B2*A2 where A2 holds the percentage (e.g. 20%) and B2 the number.

20% of 150 gives 30.

3. Percentage change between two values

=(B2-A2)/A2, formatted as %.

From 80 (A2) to 92 (B2): (92 − 80) ÷ 80 = 0.15, shown as 15%. A fall shows as a negative percentage. If A2 can be zero, wrap it: =IF(A2=0,"",(B2-A2)/A2), because a change from zero has no defined percentage.

Use ABS(A2) in the denominator if your starting values can be negative (for example, profit going from −20 to 10), otherwise the sign of the result flips.

4. Increase or decrease a number by a percentage

Increase: =A2*(1+B2). Decrease: =A2*(1-B2).

A price of 80 in A2 with 25% in B2: increase gives 100, decrease gives 60. This is how you apply a price rise, a discount or a tax rate in one step. For two discounts in a row, multiply both factors: =A2*(1-B2)*(1-C2). That is why 20% then 10% off is 28% off, not 30% — the discount calculator explains it in detail.

5. Remove a percentage that was added (reverse percentage)

=A2/(1+B2).

A price of 1,180 including 18% tax: 1,180 ÷ 1.18 = 1,000. Do not use =A2*(1-B2) here; that gives 967.60, which is wrong because the 18% was charged on 1,000, not on 1,180.

6. Each row as a percentage of the column total

=B2/SUM($B$2:$B$10), formatted as %, then fill down.

The dollar signs lock the total range, so it does not shift as you copy the formula down. Forgetting them is the most common reason a percent-of-total column comes out wrong after the first row. The percentages should add up to 100%; if they do not, check the range.

A worked example: marks to percentage

A student’s marks are in column B and the maximum for each paper in column C, rows 2 to 6.

  • Per-subject percentage in D2: =B2/C2, formatted as %, filled down.
  • Overall percentage: =SUM(B2:B6)/SUM(C2:C6).

Do not average column D for the overall figure when the maximums differ — =AVERAGE(D2:D6) gives a 50-mark paper the same weight as a 100-mark one. The marks percentage calculator shows the difference on real numbers.

Formatting tips

  • Decimal places: Excel’s % button shows 0 decimal places by default, so 12.5% displays as 13%. Use “Increase decimal” to see what is actually there.
  • Keyboard shortcut: Ctrl+Shift+% applies percentage format in Excel and in Google Sheets.
  • Rounding for display vs storage: formatting hides decimals but keeps them. If you need the stored value rounded, use =ROUND(A2/B2,4) (four decimals of the fraction = two decimals of the percentage).
  • Percentage points: subtracting one percentage cell from another (=B2-A2) gives the change in points, not a percentage change. See the percentage calculator or our guide to percentage points for the distinction.

Troubleshooting

  • Result is 100 times too big (e.g. 2500%): you multiplied by 100 and also applied % format. Remove the *100.
  • Result shows 0%: the cell is formatted with no decimals and the value is below 0.5%, or one of the inputs is text. Check with =ISNUMBER(A2).
  • #DIV/0!: the denominator is blank or zero. Use IF or IFERROR to show a blank instead.
  • Percentages do not sum to 100%: unlocked total range, hidden rows, or rounding in display. Increase decimals to check.

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