Last updated:
Quick answer
Set up two sheets, one for items and one for stock movements, and let formulas compute on-hand stock and flip a status column to REORDER when you hit your minimum. A daily email script can push the alert to you so you never have to open the sheet to know what is low.
At a glance
All outcome figures are estimates from cited sources, not independent verification by us.
- What it is allowed to do
- Drafts for you
Writes drafts (emails, posts, plans, replies). You review and send. Nothing goes out without you.
- Time saved (estimate)
- Roughly 1-2 hours per week once running, versus manual stock checks.
- Difficulty
- Intermediate
- Tools needed
- ChatGPT, Google Sheets
- Typical cost
- Google Sheets is free. ChatGPT and Claude free tiers work for generating the formulas.
Reviewed Oct 19, 2026
Basis (estimate): Estimate only: manual counting and reorder guessing across dozens of SKUs takes an hour or more weekly; a formula-driven sheet reduces it to logging movements.
What does this setup do?
Build a two-sheet inventory tracker where formulas compute stock on hand and flag reorders, with an optional daily email alert, all from free tools.
Who is it for?
Small retailers, makers, and resellers tracking tens to hundreds of SKUs who are not ready for inventory software.
How do you set it up?
Tools
- A Google account (Google Sheets is free)
- A ChatGPT or Claude account (free tier works) to generate the formulas
- Your item list: SKU, name, opening stock, minimum stock, unit cost
- Optional: a few minutes in Apps Script for the daily email alert
Steps
- Create an Inventory sheet with columns: SKU, item, opening stock, minimum stock, unit cost, and a status column.
- Create a Movements sheet: date, SKU, IN or OUT, quantity, note. Log every delivery and sale as a new row; never overwrite a number.
- Add SUMIFS formulas so the Inventory sheet totals IN and OUT per SKU, then computes current stock as opening plus IN minus OUT.
- Add the status formula: REORDER when stock is at or below minimum, a LOW warning band above that, OK otherwise; color them with conditional formatting.
- Set your reorder minimums with the AI using the reorder point formula: average daily sales times lead time plus safety days.
- Optional: add an Apps Script with a daily trigger that emails you the SKUs currently flagged REORDER.
- Test with one real SKU end to end before entering the full catalog.
Example output
Illustrative. Your results will differ.
- Your input turned into a clear, prioritized plan
- Next 3 actions with dates, in priority order
- You stay in charge. The agent just organizes.
Where to paste this prompt
ChatGPT: ChatGPT → Project instructions, or ChatGPT Tasks for scheduled reminders (once a day on Free)
Copy-paste prompt
Adapt bracketed fields to your situation.
Help me build an inventory tracker in Google Sheets with reorder alerts.
My items (SKU | name | opening stock | minimum stock | unit cost):
[paste your list]
I need:
1. The exact column layout for an Inventory sheet and a Movements sheet
2. The SUMIFS formulas to total stock IN and OUT per SKU from the Movements sheet
3. A current-stock formula (opening + IN - OUT) and a status formula that returns REORDER at or below minimum, LOW up to 1.5x minimum, else OK
4. Conditional formatting rules (red for REORDER, amber for LOW)
5. A short Apps Script with a daily time trigger that emails [email] the SKUs flagged REORDER
Rules: formulas must work in Google Sheets. Explain each formula in one line. Show me everything first; I will build it myself and test with one SKU.Newsletter
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What usually goes wrong?
Where agents tend to stall on this job. More patterns in Where AI gets stuck.
- Typing current stock directly instead of logging movements destroys your audit trail; always add a movement row.
- Stale average-daily-sales numbers make reorder points wrong; recompute from a rolling window.
- Sheets stays responsive into the thousands of SKUs, but past that move the source of truth to a database and keep the sheet as a dashboard.
- The email script needs the alert address stored safely; test the trigger before relying on it.
Which chat tools work with this prompt?
Paste the prompt into any of these assistants (free or paid tiers).
- ChatGPT
- Claude
Common questions
- How do I decide the reorder minimum for each SKU?
- Multiply average daily sales by your supplier lead time in days, then add a safety buffer of a few days. Recompute the average regularly so it tracks real demand.
- Can the sheet email me when stock is low?
- Yes, with a short Apps Script on a daily trigger that reads the status column and emails the SKUs flagged REORDER. It is optional; the colored status column works without it.
- When should I move off a spreadsheet?
- Sheets handles thousands of SKUs fine. Move to inventory software when you need multiple locations, barcode workflows at scale, or purchase-order management.
What tips make it smoother?
- Compute the reorder point as average daily sales times (supplier lead time plus safety days); refresh the average monthly so seasonal spikes move the number.
- Keep SKUs short, unique, and free of spaces so the lookup formulas never mismatch.
- Reorder against available stock, not just on-hand, if you take pre-orders or hold reservations.
Where do the claims come from?
Summaries use public sources linked below, not independent verification. How setups are picked.
- Read juangiles260 (DEV)’s write-up (dev.to)
juangiles260 (DEV): Two-sheet design, SUMIFS stock formulas, REORDER/LOW/OK status logic, and the daily email alert script pattern.
- Read WarehouseMadeSimple’s write-up (medium.com)
WarehouseMadeSimple: Reorder point formula: average daily sales times (lead time plus safety days), with a worked example.
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