How to Prevent Stockouts on Shopify Before They Cost You Revenue

A stockout is not just a missed sale — it is a compounding problem. When a product goes out of stock on Shopify, your listing gets buried in search results, customers move to a competitor, and some never come back. Studies on D2C brands in India show that a single stockout event on a top-10 SKU can cost 15–25% of that month's revenue on that product alone.

The frustrating part: most stockouts are completely predictable. Your Shopify orders export contains everything you need to see them coming 2–3 weeks in advance. The problem is that very few merchants are actually doing the math.

The most common reason merchants stock out despite watching their inventory is that they're watching the wrong number. They look at "units in stock" but not "days of stock remaining." Those are very different things.

• 300 units sounds fine — until you're selling 40/day and your supplier needs 12 days to deliver
• Sales velocity changes silently — a product that sold 5/day last month might now sell 15/day after a social media mention
• Lead times are inconsistent — that 7-day estimate from your supplier becomes 14 days during festival season
• Multiple SKUs compete for attention — you catch the bestseller but miss the mid-tier product that quietly drains

To predict a stockout before it happens, you only need three numbers for each product:

1. 1Average Daily Sales (ADS) — your units sold over the last 30 days divided by 30. Use 60 or 90 days if your sales are seasonal.
2. 2Current Stock — exactly how many units are physically available to sell right now (exclude reserved/held units).
3. 3Supplier Lead Time — realistic days from placing an order to units arriving in your warehouse, not the optimistic estimate.

If Days of Stock Remaining is less than your supplier lead time, you are already in danger. You should have reordered yesterday.

The right time to reorder is when your stock level hits the reorder point — not when you're already low. Your reorder point should account for both lead time and a buffer for demand spikes:

For safety stock, a simple starting point: multiply your average daily sales by 7 (one week's buffer). Adjust up for products with unpredictable demand or long lead times.

Doing this calculation for 3 products takes 10 minutes with a spreadsheet. For 50+ SKUs, it becomes a full-time job — and the numbers are already outdated by the time you finish.

This is exactly what Forestock automates. Export your Shopify orders as a CSV, upload it, set your lead time, and within 30 seconds you'll see which products are at risk, their exact stockout dates, how much revenue is at stake, and the specific date by which you need to place an order.

• Export your last 90 days of Shopify orders (Orders → Export → CSV)
• Calculate days of stock remaining for your top 10 SKUs
• Identify any product where that number is less than 2× your lead time
• Place reorders for those products today — not next week
• Set a weekly reminder to repeat this process

The merchants who never stock out are not luckier than you — they simply check this number before it becomes a crisis.