warning Free Tool

Stockout Calculator

See when you'll run out of stock and when to reorder. Enter your numbers below for instant results.

Average units sold per day

Days from placing an order to receiving stock

How It Works

1

We divide your current stock by daily sales to get days until stockout.

2

We compare that with your lead time to tell you if you need to order now.

3

We suggest a reorder quantity to cover lead time plus a 7-day buffer.

Automate this for your entire catalog

ReOrder AI syncs with Shopify & WooCommerce and runs stockout analysis on every SKU automatically — with AI demand forecasting.

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Frequently Asked Questions

What is a stockout?

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A stockout occurs when inventory for a product drops to zero, meaning you cannot fulfill customer orders. Stockouts lead to lost sales, lower customer satisfaction, and potential long-term revenue loss. For e-commerce businesses on Shopify or WooCommerce, stockouts can also hurt your search rankings as out-of-stock products get deprioritized.

How do you calculate days until stockout?

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Divide your current stock by your average daily sales. For example, if you have 150 units and sell 10 per day, you have approximately 15 days until stockout. This is a simplified calculation — in practice, demand can fluctuate, so you should also factor in safety stock and seasonal trends.

When should I reorder to avoid a stockout?

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Reorder when your remaining stock covers your lead time plus a safety buffer. If your lead time is 7 days and you sell 10 units/day, reorder when you have at least 100–120 units (lead time demand + 3–5 day buffer). The exact reorder point depends on demand variability and how critical the product is to your revenue.

How much does a stockout cost?

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Research shows stockouts cost retailers up to 4% of annual revenue. Beyond direct lost sales, stockouts damage brand loyalty — 21–43% of customers will switch to a competitor when their preferred product is out of stock. For a $1M/year e-commerce store, that could mean $40,000+ in annual losses from stockouts alone.