Forecast inventory and auto-generate reorders with Google Sheets, GPT-4o mini and Slack

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Built by Redowan Ahmed Farhan Redowan Ahmed Farhan
Created on June 10, 2026

Description

How it works

Fetches sales history and current inventory from Google Sheets in parallel, then calculates days of stock remaining, average daily sales velocity, and projected stockout dates for every product
An AI agent (GPT-4o mini) analyzes the snapshot and generates a structured forecast report covering critical alerts, reorder priorities, demand trends, and supply chain risk flags
Routes critical stock alerts to Slack instantly, generates purchase orders for all flagged items, and logs the full forecast summary back to Google Sheets

Set up steps

Connect Google Sheets OAuth2, add your spreadsheet ID in Set Forecast Configuration, and ensure your sheet has Sales_History, Current_Inventory, and Forcast_Analysis tabs (~5 min)
Add your OpenAI API key and connect your Slack workspace, then point the alert node to your preferred channel (~5 min)

Nodes Used (5)

AI Agent
@n8n/n8n-nodes-langchain.agent
Code
n8n-nodes-base.code
Google Sheets
n8n-nodes-base.googleSheets
OpenAI Chat Model
@n8n/n8n-nodes-langchain.lmChatOpenAi
Slack
n8n-nodes-base.slack