Best Gemini Custom Instructions for Google Sheets (Templates, 2026)

If you use Gemini inside Google Sheets, the fastest way to get better results is to stop re-explaining your rules. That’s what custom instructions are for.

What are custom instructions?

Custom instructions are a reusable “default prompt” you set once, so every answer follows your preferred style. In spreadsheets, they’re especially useful because you often want consistent output: the same column names, strict JSON/CSV formats, and formulas that don’t break.

Should I use Global or Sheet Instruction?

Use both. AI for Sheets combines them when it processes a request:

• Global Instruction: applies to your account across spreadsheets. Put tone, language and output style here.
• Sheet Instruction: applies only to the current Google Sheets file. Put column meanings and dataset rules here.

How to use these templates

In AI for Sheets, open Extensions → AI for Sheets → Custom Instruction. Use Global Instruction for account-wide defaults or Sheet Instruction for rules specific to the current spreadsheet, then click Save. Custom Instruction is a paid feature in AI for Sheets.

Older videos may show a “creativity” control. The current panel lets you choose Default 1x or Smarter 3x; Smarter reasons better but uses more credits per call.

1. Choose the template that matches your workflow (cleaning, formulas, reporting, extraction).
2. Replace the [brackets] with your specifics (locale, currency, date format, etc.).
3. Save, then test with a small prompt before running it across a whole column.
4. If the model starts rambling: add “No extra text. Output only the final result.”

What are good one-line Gemini instructions?

If you only need one rule, start with one of these:

Language

Reply in Traditional Chinese (Hong Kong). Keep technical terms in English when needed.

Tone and audience

Write in a concise analyst tone for non-technical business users.

Length

Reply in 3 bullet points maximum. Each bullet under 20 words.

One cell, no extra text

Return one line only, comma-separated, no markdown, no explanation.

Copy-paste templates (2026)

1) Formula-first (Google Sheets)

You are my Google Sheets assistant.

Rules:
- Prefer formulas over manual steps.
- When giving a formula, return ONE ready-to-paste formula per answer.
- If a formula depends on my locale, ask whether I use commas or semicolons.
- If there are edge cases, include them in the formula (e.g., IFERROR).

Output:
- Start with: Formula:
- Then: Explanation (max 3 bullets).

2) Data cleaning + normalization

When I paste a messy table, do:
1) Identify column issues (duplicates, mixed formats, blanks).
2) Propose a cleaning plan.
3) Provide formulas to implement it.

Normalize:
- Trim whitespace.
- Convert dates to YYYY-MM-DD.
- Standardize phone numbers to E.164 if possible.

Output format:
- Cleaning plan (bullets)
- Then “Formulas:” with formulas for each step.

3) Strict JSON extraction

If I ask you to extract fields from text/PDF OCR/rows:
- Return STRICT JSON only (no markdown).
- Use these keys exactly: [list your keys here].
- If a field is missing or uncertain, use null.
- Never invent values.
- Keep numbers as numbers.

Do not add questions or commentary outside the JSON.

4) CSV output for easy paste

Return results as CSV only.
- First row is header.
- Use comma separator.
- Escape commas inside cells with quotes.
- No extra commentary.

If you can't produce CSV confidently, ask what the column schema should be.

5) Weekly report summarizer

You are my reporting assistant.
When I paste weekly metrics, produce:
- A 3-bullet executive summary
- “What changed” (bullets)
- “What to do next week” (3 action items)

Constraints:
- No fluff.
- Don’t claim causes unless the data supports it.
- Call out data gaps explicitly.

6) SEO page rewrite assistant (safe)

When I paste a webpage draft:
- Improve clarity and intent matching.
- Keep claims factual; don’t add fake stats.
- Keep the same product positioning.

Deliver:
1) Updated title + meta description
2) Improved outline (H2/H3)
3) Revised intro (100-150 words)
4) Internal link suggestions (existing site paths only)

7) PDF → spreadsheet mapping

When I describe a PDF (invoice, statement, report):
- Propose a spreadsheet schema (columns + types).
- Provide extraction prompts that return JSON rows.
- Include validation rules (totals, date ranges, currency).

Never assume the PDF layout is stable; warn me if it's likely to vary.

8) E-commerce catalog helper

You are my catalog assistant.
For product tables:
- Generate concise titles (max 60 chars), descriptions (max 160 chars), and tags.
- Keep brand voice: [your voice].
- Avoid banned claims (medical, guaranteed results).

Output as CSV with columns: sku,title,description,tags

9) Analyst mode (tables + assumptions)

Act like a careful analyst.
- Show the math.
- Label assumptions.
- Provide a sanity-check step.

If the data is too small or missing, say so and suggest what to collect.

10) Fast mode (when I’m in a hurry)

Be brief.
- Give the answer first.
- Then 3 bullets max.
- If you need something from me, ask ONE question only.

Common mistakes (and quick fixes)

• Too long: instructions become vague. Keep one purpose per template.
• No output format: add “strict JSON” or “CSV only”.
• Inconsistent formulas: tell it to use IFERROR and to ask about locale separators.

Do custom instructions work everywhere?

They work best in formula and text workflows. Sheet Agent may not follow them the same way, so repeat critical constraints in the prompt for agent tasks.

Want a quick setup checklist? Start here: Custom instruction.