Google Sheets™ Error Checker for Reports You Need to Trust

The visible Google Sheets™ errors

Google Sheets surfaces formula errors as red triangles or in-cell error tokens. Detector Set v0.4 catches the common visible cases when they come from formula cells:

The manual way: Find & Replace

Open the Find dialog with Ctrl+F on Windows or Cmd+F on Mac. Click the three-dot icon to reveal advanced options, check "Also search within formulas", and run searches for each error token. Cycle through hits with Enter, fix in place. Works fine for small sheets.

The reason Find & Replace alone is not enough: it only finds the visible errors. The bugs that cause the worst real-world damage are silent.

The silent bugs Find & Replace cannot catch

Silent bugs return a number that looks right but is wrong. None of them light up in red. None of them appear in Find & Replace. They are the reason automated error checkers exist:

Mixed data types in a number column

You have a "Revenue" column with 500 rows. Most are real numbers. A few rows were pasted from email and are text strings that look numeric — "15,000", "15K", "$15000". SUMIFS, COUNTIFS, and AVERAGEIFS silently exclude the text ones. Your monthly total is 83% of what it should be and nobody catches it.

Manual detection: in an empty cell, run =COUNTA(F2:F10000) - COUNT(F2:F10000). The result is the number of non-numeric, non-empty cells in column F.

Duplicate keys in a lookup column

VLOOKUP and XLOOKUP return the first match they find. If your customer-ID column has 500 unique IDs and 4 accidental duplicates, 4 lookups in the rest of the sheet have been returning the wrong row forever — every time the sheet recalculates.

Manual detection: =COUNTIF(A:A, A2) in a helper column, then conditional-format any cell > 1 in red.

Formula pattern outliers

A formula-filled column usually has a repeated pattern: row 2 references row 2, row 3 references row 3, and so on. One copied-over row can silently break that pattern. Detector Set v0.4 flags conservative same-column outliers, and it also flags missing copied formulas when two matching formulas sit immediately above and below a hardcoded or blank cell.

Formula drift after column moves or renames (handled by Repair, not Check)

Someone inserted a column before F. Your =SUM(F:F) now sums whatever moved into F, not the original Revenue column. Or someone renamed the "Amount" header to "Revenue" — the formula still works, but the meaning shifted under it. This bug class leaves no visible mark. Every cell has a value. The numbers are just wrong.

Manual detection: keep a locked reference sheet of the original layout and compare periodically. Most teams do not. SheetBrain's Repair tab is purpose-built for this case — it captures a schema snapshot and proposes safe formula rewrites when columns move or get renamed. Repair is part of the $9/mo Pro plan and is separate from the Check detectors below.

How SheetBrain checks for errors

SheetBrain is a free Google Sheets™ add-on. The error checker is the Check tab in the sidebar:

1. Install from the Google Workspace Marketplace. Free Gmail™ supported.
2. Open any Sheet, then Extensions › SheetBrain › Open.
3. Click the Check tab. Scan runs automatically on the active sheet.
4. Review the findings list. Each item shows the affected cell, the issue type, the severity (error or warning), and a proposed fix where one is available.

For users who live in the formula bar, the same scan is a custom function. Pass the range as an unquoted reference (a quoted string is rejected):

Returns a 0–100 score string like "87 — 2 issues" directly in the cell. The score starts at 100 and drops 15 per error and 5 per warning, with a floor at 0; "100 — All clear ✓" means no findings. Combine with =SHEETBRAIN_ISSUES(A1:Z1000) to spill a Cell / Issue / Severity / Description table. Tip: pass NOW() as a second argument to force a refresh.

What Detector Set v0.4 actually runs

• broken_reference — severity error. Flags cells displaying #REF!, plus VLOOKUP/HLOOKUP/INDEX calls whose column or row index argument exceeds the referenced range. The lookup-index case ships with an auto-fix that clamps the index to the range span. The #REF!-display case does not auto-fix because the original target is gone.
• visible_formula_error — severity error. Flags formula cells returning #N/A, #VALUE!, #DIV/0!, #NAME?, #NUM!, #NULL!, or #ERROR!. Literal text values are ignored.
• mixed_text_number — severity warning. Column-level type analysis. Flags columns mixing numeric and text-stored values, the common SUMIFS / COUNTIFS / AVERAGEIFS silent-skip cause.
• duplicate_lookup_key — severity warning. Flags lookup-key columns containing duplicate values when used by VLOOKUP or XLOOKUP, since those formulas silently return the first matching row.
• inconsistent_formula_pattern — severity warning. Flags one-off formula deviations inside repeated same-column formula runs when a clear majority pattern exists.
• missing_formula_pattern — severity warning. Flags hardcoded or blank cells inside repeated formula columns when two formulas above and two formulas below all match the same pattern.

That is the entire v0.4 detector set. Schema drift and formula drift after column moves remain Repair features, not Check detectors. The full detector definitions, severity classes, scope limits (1,000 rows × 50 columns per sheet), and content hash are pinned at the SheetBrain Detector Set v0.4 reference page.

Frequently asked questions