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Google Sheets percentage formulas for totals, growth and discounts

Calculate a share of total, percentage growth, discounts and percentage-point differences.

PhilisWritten by PhilisPublished June 21, 2026Last updated July 25, 202611 min
Google Sheets percentages — SheetSteps
QUICK ANSWER

Use =part/total for a share, =(new-old)/old for percentage growth and =price*(1-discount) for a discounted price. Apply percent formatting after the calculation.

Before you calculate percentages with the right denominator, set up a clean source range and one result you can check by hand. That gives you a known answer before the sheet grows.

This article shows how to calculate percentages with the right denominator. The sample sheet uses ordinary rows so you can copy the method into an existing file without rebuilding everything.

Google Sheets percentages spreadsheet used in this article
A working sheet built for this article. The numbers are sample data.
01
INSTRUCTIONS

Google Sheets percentage formulas for totals, growth and discounts

  1. 01
    Make a safe copy

    Duplicate the source tab or file before changing formulas, ranges or formatting.

  2. 02
    Set up the source rows

    Add the fields needed to calculate percentages with the right denominator. Keep one record on each row and one field in each column.

  3. 03
    Add the method

    Enter =(C2-B2)/B2 in a test cell and check its first result.

  4. 04
    Check a known case

    Pick one row whose answer you already know and compare it with the sheet result.

  5. 05
    Test the awkward rows

    Check blanks, zeros, repeated entries and one row that should not match.

  6. 06
    Apply it to the full range

    Copy the formula or rule only after the sample cases return the expected result.

02
FORMULAS

Set up the sheet for Google Sheets percentages

Keep the source table rectangular. A single header row, no merged cells and consistent cell types make the work much easier to check.

Place settings, fixed rates or allowed labels on a separate tab. Name them clearly so another person can read the file without tracing every cell.

  • Choose the correct denominator
  • Handle a zero starting amount
  • Separate percent and percentage points
  • Apply percent format once
03
FORMULAS

Check the first result before copying it

A result that looks plausible can still be wrong. Work through one row manually, compare it with the Sheet and check every referenced cell.

Next, test a blank row and an unusual row. These two checks catch many range, type and copied-reference mistakes before they spread.

fx=(C2-B2)/B2
04
FORMULAS

Keep the file reliable as new rows arrive

Leave input columns visually separate from calculated columns. Protect formulas when several people edit the same file, and keep dropdown lists or settings outside the main table.

Add a short check near the result: row count, unmatched count, last refresh time or a manual spot check. The right check depends on the job, but it should make a bad update easy to notice.

05
COMMON QUESTIONS

Questions people ask

How do I calculate a percentage of a total?＋

Divide the part by the total, then format the result as a percentage.

How do I calculate percentage increase?＋

Use =(new-old)/old. Check the case where old equals zero separately.

Why does 20% show as 2000%?＋

The formula may already multiply by 100 before percent formatting. Remove that multiplication.

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