How to prevent FBA stockouts with days-of-cover alerts

Why unit counts fool you

"I still have 300 units, so I'm fine" is a dangerous sentence. If you sell 30 units a day, 300 units gives you ten days of cover. If you sell 100 units a day, the same 300 units gives you three. The unit count alone never tells you how fast stock is disappearing — only how much is left.

A stockout costs far more than lost sales. It erodes your Best Seller Rank, suppresses your Buy Box, and can take weeks to recover — often longer than the stockout itself. Restocking on unit counts instead of consumption is one of the most common and most preventable causes.

What days of cover actually means

Days of cover is the answer to one question: at today's sales rate, how many days until this SKU sells out? It is your available inventory divided by your daily sales velocity.

The moment days of cover becomes useful is when you compare it to your supplier lead time — the number of days between placing a purchase order and your stock arriving at an Amazon fulfillment center. If your lead time is 45 days and your cover is 30 days, you are already too late.

The reorder rule that prevents stockouts

1. Know your lead time. Track the real gap between ordering and receiving — average, median, and worst case. ReplenishIQ computes this from your actual shipment and receipt history, so you are not guessing.
2. Know your velocity. Use a 30/60/90-day window so one spike or lull does not distort the picture.
3. Reorder when cover drops below lead time plus a safety buffer. The buffer absorbs supplier delays, freight variance, and demand surges.

The rule is simple: order before your days of cover falls below your lead time. ReplenishIQ automates this comparison and flags every SKU that is about to cross the line.

How ReplenishIQ makes this automatic

Instead of opening spreadsheets, ReplenishIQ watches every SKU for you:

• Days of cover is calculated continuously from synced inventory and shipment-based sales velocity — no manual math.
• Lead time is measured from real data, not estimates, so the reorder threshold reflects how your supply chain actually behaves.
• Smart alerts fire when cover approaches lead time, with severity set by how close you are to the edge — a warning while there is still time, and a critical alert when reordering is overdue.
• Days-to-stockout is shown up front, so you and your team act on the number that matters, not a raw count.