FBA reorder point: when to reorder so you never stock out

Your FBA reorder point is the stock level that tells you to place your next purchase order: average daily sales × total lead time in days + safety stock. When your available plus inbound units fall to that number, you order. The part most sellers get wrong isn’t the formula. It’s the lead time, which runs from the day you place the order until units are actually buyable on Amazon.

What is the reorder point formula?

There are only three inputs:

• Average daily sales. Units per day, not revenue. Use a recent window, such as the last 30 days, and sanity-check it against the last 90.
• Total lead time. Days from placing the purchase order to units being available for sale on Amazon.
• Safety stock. Extra units to cover slower-than-usual freight, a sales spike, or Amazon taking longer to check in your shipment.

Put together: reorder point = daily sales × total lead time + safety stock.

Then compare it with what you actually have: units available in FBA, plus units in transit or being received, plus units already on order. If that total is at or below the reorder point, it’s time to order.

What counts as lead time for FBA?

This is where the math usually breaks. Sellers write “lead time: 30 days” because that’s what their factory quoted. But the factory quote only covers one step. Add up all of them:

Amazon receiving is the easiest step to forget and one of the least predictable. Small parcel shipments often check in quickly. Pallets and shipments during Q4 can sit for a while. Use what you’ve actually seen from your own shipments, and add extra if you’re shipping into a busy season.

If you use a 3PL or Amazon Warehousing and Distribution as a buffer, count the time to move stock from there into FBA too. For how the shipment step works, see our Send to Amazon shipment guide.

Worked example: calculating a reorder point

For example, say you sell a kitchen gadget made overseas. These numbers are round and made up to show the math:

• Average daily sales: 20 units
• Order and deposit: 5 days
• Production: 30 days
• Ocean freight, customs and trucking: 35 days
• Prep and shipment creation: 5 days
• Transit to Amazon: 5 days
• Amazon receiving: 10 days

Total lead time is 5 + 30 + 35 + 5 + 5 + 10 = 90 days. That’s three times the “30-day lead time” the factory quoted.

Lead-time demand is 20 units × 90 days = 1,800 units. Add safety stock of three weeks, 20 × 21 = 420 units.

Reorder point = 1,800 + 420 = 2,220 units.

So when available, inbound and on-order units together fall to about 2,220, you place the next order. If you’d used the factory’s 30 days, your reorder point would have been 600 + 420 = 1,020 units, and you’d have run out for weeks.

How much should you order?

The reorder point tells you when. The quantity is a separate question. A simple way: order enough to cover the time until your next order would arrive, usually 60–120 days of sales for a small brand, adjusted for your supplier’s minimum order and your cash. In the example, 90 days of cover at 20 a day is 1,800 units.

How much safety stock is enough?

Safety stock is insurance, and like all insurance it costs money: cash tied up and storage fees. Size it to the risk you actually face:

• Stable supplier, steady sales: about 2 weeks of sales is often enough.
• Freight that slips, or sales that swing with ads or deals: 3–4 weeks.
• Heading into Q4 or a big deal event: more, because both demand and receiving delays go up at the same time.

A useful check: look at the worst delay you had on your last few orders. If one shipment arrived three weeks late, your safety stock should cover at least that.

Stocking out on Amazon hurts more than the lost sales. Your listing can lose ranking and ads stop serving while you’re out. It often takes a while to climb back after you restock. That’s why a little extra safety stock is usually cheaper than the alternative.

Why not just send way more inventory?

Because Amazon charges you for keeping it, and limits how much you can send.

• Storage fees. You pay monthly storage per cubic foot, and rates go up in October–December. Inventory that sits long enough also picks up aged-inventory surcharges. Check current rates in Seller Central Help by searching “FBA monthly storage fees.”
• Capacity limits. Amazon caps how much inventory you can have in FBA based on things like your sales and Inventory Performance Index. As of September 2026 these limits are set monthly, and you can see yours in Seller Central’s Capacity Monitor. If you’re near the limit, a big shipment may not fit.
• Low-inventory fee. The opposite problem also costs money. As of September 2026, Amazon charges a low-inventory-level fee on units shipped when a product’s historical days of supply falls below 28 days. Search “low-inventory-level fee” in Help for details.

The sweet spot is to keep FBA stocked with roughly 1–3 months of sales and hold the rest upstream, at your 3PL or prep center, where storage is usually cheaper and you can replenish as needed.

How do you handle seasonality?

The formula uses “average daily sales,” but the average that matters is the one during the lead time you’re ordering for, not last month’s. If you’re placing an order in August that will sell in November, use your expected November sales.

• Look at last year’s sales by month, if you have them, and scale by how much you’ve grown.
• Plan for Amazon’s longer receiving times and earlier inventory deadlines before Prime Day, Prime Big Deal Days and Q4.
• If you’re running a deal, add the expected deal lift on top. Our Prime Exclusive Discounts guide covers planning units for an event.
• After the peak, drop your daily sales estimate back down so you don’t reorder for a January that looks like December.

A simple weekly reorder routine

It takes a few minutes per SKU once it’s set up. It fits naturally into the weekly Amazon checklist.