Conditional formatting slowing down Google Sheets™? Merge the fragments

By Paul Kemp · Published 5 October 2026

One conditional formatting rule is cheap. Fifty rules are not, and that is what most older sheets end up with: every copy, paste, insert and delete can split a rule's range, leaving fragments behind. Open the rules panel on a slow sheet and you may find the same rule repeated dozens of times over scattered ranges.

See the damage

1. Open Format → Conditional formatting.
2. Count the rules, and look at their ranges. Fragments look like A2:A9, A11:A40, A42:A100: one rule Logic, many ranges.
3. Look for rules applied to entire columns (A:Z), and for duplicates doing the same job twice.

Merge them back

1. Delete rules that no longer do anything, and duplicates of rules that remain.
2. For fragmented ranges, edit the rule and replace the scattered ranges with one continuous range covering the data.
3. Narrow whole-column rules to the data. Formatting a million cells to colour a thousand is pure overhead.
4. Prefer a few simple rules over many clever ones. Each rule is evaluated separately on every change.

Find every slow rule

Sheet Speed Checker™ grades a Google Sheets™ file and shows where the time goes, including fragmented and whole-column formatting rules. Checking the active sheet, the grade, every finding and Undo are free.

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Google, Google Sheets™ and Google Workspace™ are trademarks of Google LLC. Sheet Speed Checker is not affiliated with or endorsed by Google.