# How do I calculate a percentage in a spreadsheet?

To calculate a percentage in a spreadsheet, divide the part by the whole, for example =B2/C2, then format the cell as a percent (in Google Sheets, Format > Number > Percent), so 0.25 shows as 25%. For percent change, use =(new-old)/old. ProfitDrawer's Monthly Summary works out each month's margin as profit divided by income and shows a blank instead of an error when income is 0.

**Common percentage formulas** (B = part or new value, C = whole or old value):

| Goal | Formula | Example |
|---|---|---|
| Part of a total | `=B2/C2` | 300 / 1,200 = 25% |
| Percent change | `=(B2-C2)/C2` | (1,500 - 1,200) / 1,200 = 25% |
| A percent of an amount | `=C2*0.25` | 25% of 1,200 = 300 |
| Share of a column total | `=B2/SUM($B$2:$B$100)` | each row's share |

**Show it as a percent:** select the cells and click **Format > Number > Percent**. Sheets treats 1 as 100%, so a result of 0.25 displays as 25%. The `TO_PERCENT` function does the same thing inside a formula.

**Avoid #DIV/0!:** Google notes the divisor cannot equal 0. Use `=IF(C2=0,"",B2/C2)` to show a blank until the whole has a value.

**Profit margin example:** profit 2,000 on income 8,000 gives =2000/8000 = 25%.

In ProfitDrawer workbooks, Top Clients shows each client's share of the year's income the same way, and the tax set-aside is the percent you type on Settings multiplied by profit.

- Source: [TO_PERCENT function: Google Docs Editors Help](https://support.google.com/docs/answer/3094284)
- Updated: 2026-10-29
- Published: 2026-10-29
- Category: Google Sheets and Excel how-tos
- Canonical: https://profitdrawer.com/answers/how-do-i-calculate-a-percentage-in-a-spreadsheet.html
- Publisher: ProfitDrawer (https://profitdrawer.com)