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Why is my Google Sheet™ so slow? 12 causes and how to find yours

By Paul Kemp · Published

Every edit takes seconds to settle. Scrolling stutters. The file worked fine last year. Slow Google Sheets™ files are rarely slow for mysterious reasons: the cause is usually one of twelve things, and most of them are fixable in minutes once found.

The 12 causes

  1. Lookups over whole columns. VLOOKUP(A2, B:Z, ...) scans millions of cells. Narrow every range to the data.
  2. Volatile functions. NOW(), TODAY() and RAND() recalculate on every change, anywhere in the file.
  3. Too many IMPORTRANGE calls. Each one is a separate fetch from another file.
  4. IMPORTRANGE chains. File A imports from B, which imports from C. Every edit ripples down the chain.
  5. Fragmented conditional formatting. Dozens of small rules, often split by pasting, each evaluated separately.
  6. Formatting over whole columns. Conditional formatting or data validation applied to entire columns multiplies the work.
  7. Unused rows and columns. Thousands of blank-but-formatted rows still count toward the file's size.
  8. Full-column array formulas. An ARRAYFORMULA over an entire column calculates hundreds of thousands of cells.
  9. Heavy QUERY, FILTER, SORT or UNIQUE over big ranges. Powerful functions, priced accordingly.
  10. Dense cross-tab references. Many tabs all reading from each other means every edit recalculates widely.
  11. Iterative calculation left on. Check File → Settings → Calculation: it makes every recalculation run multiple times.
  12. Sheer size. A file nearing the workbook's cell limits will always feel heavy. Split it before it gets there.

Find yours first, fix second

Work down the list: check your lookup ranges, search for NOW() and TODAY(), open Format → Conditional formatting and count the rules, and press Ctrl+End on each tab to see how far the used range really goes. Fix what you find before reaching for a bigger solution.

About two minutes on a real sheet. The full walkthrough is on YouTube.

Get the full diagnosis

Sheet Speed Checker™ grades a Google Sheets™ file and shows where the time goes, finding by finding. 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.