When to reorder on Amazon: a simple reorder point for wholesale

Running out of a product that sells is one of the most expensive mistakes in wholesale, and it rarely looks like a mistake at the time. The product was fine and the supplier was fine. The reorder just went in a week too late, and for the next two weeks the sales went to someone else.

The fix is one number per product: the reorder point. This guide shows how to work it out, which days to count in your lead time, how much to order once you reach it, and why Amazon's own restock suggestions can land somewhere else. It is for products you have already sold, where your own sales tell you the pace. For a product you have never sold, start with your first wholesale order, which sizes a test buy from listing data.

The reorder point formula

The reorder point is the stock level for one product at which you place the next purchase order, so the new units become sellable before the old ones run out.

Reorder point = units sold a day × (lead time in days + safety stock in days)

• Units sold a day is your sales pace on this product, from your own orders. Monthly sales divided by 30 works if you think in months.
• Lead time is the days from deciding to reorder until the new units are available to buy at Amazon. The next sections break it down.
• Safety stock is extra days of stock for when something runs late or sales jump.

When the stock you own falls to the reorder point, you order. If every step takes as long as usual, the new units go live just as you dip into your safety stock. If something runs slow, the safety stock covers the gap.

Count everything you own, not just what is available

Compare the reorder point with everything you own for that product, wherever it sits: units available at Amazon, units in shipments on their way in, units at your prep center, and units on a purchase order your supplier has not delivered yet. Leave out the last three and you reorder the same units twice. Amazon has no way to know about a pallet at your prep center or an open order with your distributor, so those are yours to add, whatever any report says.

Safety stock: how many days to add

Safety stock is there for two things: a lead time that runs long and sales that run fast. The simplest way to hold it is in days, which is how the calculator below works.

1. Start with your slowest recent order. If your usual lead time from a supplier is 19 days and the slowest of your last few orders took 23, four days is a sensible floor.
2. Add a little for sales swings. If your daily sales jump around from week to week, add a few days. If the product sells the same every week, you need less.
3. Add more where a step is out of your hands. A supplier that ships once a week, a long freight leg or a prep center that has run behind before all deserve extra days.

A common textbook version puts both risks in one line: the longest lead time you have seen times your highest daily sales, minus your usual lead time times your usual daily sales. Suppose your usual is 19 days at 12.5 a day and your worst recent case was 23 days at 15 a day. That gives 345 minus 237.5, about 108 units, or close to nine days at your usual pace.

Every extra day of safety stock pays storage. But it is also what keeps a steady seller above the low-inventory line, as the fees section shows, so a few days usually earns its keep.

Reorder point calculator

Type your units sold a day, your lead time, the safety days you want and everything you own now: at Amazon, on the way in, at your prep center and on open purchase orders.

You get your reorder point, your days of cover today and roughly how many days until you should reorder. If your stock covers fewer days than your lead time, the calculator says so, because at that pace you may run out before a new order can arrive.

Lead time, prep days and inbound days

Lead time is where most reorder math goes wrong, because it is easy to count only the supplier's part. In Apex University's Restocking lesson, Stef counts the whole chain:

"The first thing we need to understand is our supply chain. So this includes the lead time from our suppliers from the moment that we place the PO until the inventory arrives at our warehouse or prep center. The days of prepping time [...] and of course, the time that it takes for the inventory to arrive and be sellable within our Amazon account."

From Stef's lesson (Restocking, at 0:31)

His example adds 12 days from the supplier, 3 days of prep and 4 days to reach Amazon and become sellable: a lead time of 19 days. Yours will be different, so measure each part.

A few habits turn a lead time on paper into a real one:

• Count prep every time. From January 1, 2026, Amazon stopped prepping and labeling FBA units in the US, so every unit has to arrive ready, and your prep center's days are part of every reorder. Our log of Amazon rule changes covers what changed.
• Use the last units, not the first. Your lead time ends when the last units you are counting on are available, not when the first box is scanned.
• Count how often you look. If you check stock every Monday, a product can cross its reorder point on Tuesday and wait six days before you notice. Check fast sellers more often, or add the days between your checks to their lead time.
• Ship the way you usually ship. How you send stock in, and the placement option you pick in Send to Amazon, change both the days and the cost. The inbound placement fee guide explains the options.
• Round up. Later in the same lesson, Stef's advice on prep days is to stay conservative: if your prep center quotes two days, count three (Restocking, at 9:24). The same goes for every part of the chain.

Keep a lead time for each supplier, not one number for the whole business. A distributor two states away and a brand that ships once a month need different reorder points, even for products that sell at the same pace.

Days of cover

Days of cover tells you how long your stock lasts at your current pace.

Days of cover = units you own ÷ units sold a day

It is the quickest health check there is. Shorter than your lead time, and you are already late: even if you order today, you will be out of stock for the difference. Far longer than your lead time plus a month or two, and you are probably paying to store stock you did not need yet.

Which sales number to use

Your daily sales figure carries the whole calculation, so pick it with care.

• Compare a short window with a long one. The last 7 days catch a change quickly but one big order can throw them off. The last 90 days are steady but hide a trend that started last month. If your last 7 and last 30 days are close, use either. If they are far apart, find out why before you reorder: a price change, a competitor who ran out, or the start of a season.
• Leave out days you were out of stock. If you sold 300 units in a month but were out of stock for 10 days of it, your pace was 15 a day, not 10. Divide by the days you had stock, or your next order will be too small and you will run out again.

Your pace depends on the listing, not just the product

On a wholesale listing you share the sales with every other seller on the offer, so your pace moves when they do. Before any restock, Stef's first step is to look at the listing again:

"So we first need to always recheck your competitors. How much or do they have products in stock? Is the price changing? [...] Because, yes, our sell-through rate may be twelve point five, but maybe that number could be higher or lower depending if new sellers are joining in, if the price is dropping, are you able to compete on that price?"

From Stef's lesson (Restocking, at 4:18)

If new sellers have joined, or the price has dropped below what you can match, your share of the Buy Box and your daily sales will fall, and so should the order. If a big seller has run out, you may sell faster for a while. The Keepa charts guide shows how to read offer counts and price history before you buy.

How many days of cover to aim for

There is no single right number, but there are a few lines worth knowing.

In the lesson, Stef says he would always set 30 days of cover by default, however much cash is in the bank, with 15 days as an option when cash is tight (Restocking, from about 9:44). Either way, check your fast sellers against the 28-day line covered below: if each order brings 30 days of cover and you keep only a few safety days, your average stock can sit under it.

How much to order when you reach it

The reorder point tells you when. The order quantity tells you how much. Work it out for the cover you want once the new units land:

Order = units sold a day × (lead time + safety days + days of cover you want) − units you own now

Order right at your reorder point and this comes out to your daily sales times the days of cover you want. Order later and it grows to make up the difference. Then adjust it for the real world:

1. Round up to full cases. Many distributors sell only by the case pack. Round up to whole cases, because rounding down leaves you short before the next order.
2. Check the supplier's minimum. If one product's reorder does not reach the order minimum, bring forward other products from the same supplier that are close to their own reorder points, rather than overbuying one. Stef does this in the lesson, adding products to a restock purchase order to meet a supplier's minimum.
3. Ask about a volume price. A reorder is the best time to negotiate, because the supplier now knows you pay. A bigger order only makes sense if the discount saves more than the extra months of storage cost. The negotiation guide has scripts for it.
4. Recheck the profit. Prices and fees move between orders. Run the reorder through the profit calculator with your landed cost per unit (the supplier price plus freight, prep and inbound fees) at today's Buy Box price.
5. Check the cash. You pay the supplier weeks before the units sell, and Amazon pays you out later still, after delivery. The cost to start guide covers keeping money back for reorders.

A worked example

Here is the example from the Restocking lesson, worked through with the formulas on this page. Stef uses example numbers on a product he used to resell (Restocking, from 1:01 to 3:36). He has 81 units at Amazon, selling 12.5 a day, and a lead time of 19 days: 12 from the supplier, 3 for prep and 4 into Amazon.

1. Days of cover. 81 ÷ 12.5 = 6.48 days. Stef rounds it to a whole 7 days:

   "I rounded up to seven because warehouses are not robots, sales reps are not robots, you're not a robot."

   From Stef's lesson (Restocking, at 2:06)

   Rounding days of cover up makes your stock look a little longer-lasting than it is. In your own planning, round days of cover down and lead times up, so any error leaves you early rather than late.

2. Reorder point. With no safety stock, 12.5 × 19 = 237.5, rounded up to 238 units. He has 81, so he is 157 units under it. He should have ordered when he had 238, about 12 days of sales earlier, which is Stef's conclusion in the lesson too: the order should have been placed twelve days ago.

3. What being late costs. The new stock takes 19 days and the old stock lasts about 7, so the product is out of stock for about 12 days. That is 12 × 12.5 = 150 missed sales. At the $2.16 profit per unit in his example, it is $324 of missed profit on one product from one late order. That is one example with example numbers; yours will differ, but the math is the same.

4. How much to order. Stef's target is 30 days of cover. He works out the stock he needs as 12.5 × (30 + 19) = 612.5, rounded up to 613 units. Take off the 81 units already there and the order is 532 units.

5. Round to cases. If this product came in cases of 12 (an assumption for the example), 532 rounds up to 540 units, or 45 cases.

One catch when you are already late. The 613 assumes you keep selling all through the lead time. Here you can't: you will be out of stock for about 12 days, and those 150 sales never happen. So the 540 units land on an empty shelf and last about 43 days, not 30. That is not wrong, but it is more stock than the target. If cash is tight, order for the cover you want after the units land: 12.5 × 30 = 375 units, or 384 in cases of 12.

The same product, on time. Now suppose you own 500 units, counting what is on the way, and you want 5 days of safety stock. Your reorder point is 12.5 × (19 + 5) = 300 units, and your days of cover are 500 ÷ 12.5 = 40. You reach 300 units in (500 − 300) ÷ 12.5 = 16 days, so that is when you order. Order 375 units for 30 days of cover, and they land when you are down to about 63 units, your safety stock, leaving about 35 days of stock. Type the same numbers into the calculator above to check.

The fees on either side of your reorder point

Your reorder point and order size decide how much stock you hold between orders, and Amazon charges for getting that wrong in both directions. The storage fees guide has the detail on every fee below.

Too little stock

Lost sales come first. In a Seller Forums post on FBA inventory tools, Amazon staff wrote: "Running out of stock can mean lost sales, lower search rankings, and frustrated customers." The worked example shows how fast lost sales add up, and a product that slips in search can take a while to sell at its old pace again.

Then the low-inventory-level fee. When Amazon introduced the fee for 2024, staff explained in a Seller Forums post that it applies only to standard-size products, and only when a product's historical days of supply is under 28 days in both the short-term window (the last 30 days) and the long-term window (the last 90 days). For products you replenish yourself, the same post suggests sending in enough units that the short-term figure goes over 28 days. Amazon's current help page for the fee needs a Seller Central sign-in, and some details have been reported to have changed since, so check the storage fees guide and the Historical days of supply column on your FBA Inventory page.

Here is the part that matters for reorder planning. Amazon describes days of supply as your inventory levels relative to your actual sales over those windows, so what counts is your typical stock level between orders, not your stock on the day you reorder. With steady sales and on-time arrivals, your stock swings from your safety stock (just before an order lands) up to safety stock plus the days that order covers, and the average sits about halfway between.

This is our simple model, not Amazon's formula, and real sales are never this steady. But it shows something that catches people out: ordering more often keeps less stock in Amazon's warehouses, which saves storage, and it also pulls your average days of supply down toward the line. A fast seller you reorder every two weeks needs more safety stock than you might think.

Too much stock

Monthly storage. Amazon charges storage every month for the space your units take up, worked out from your daily average volume in cubic feet. Each extra day of cover is an extra day of storage on every unit, and the rate is higher from October to December.

Excess inventory. Amazon's inventory management guide lists over 90 days of supply, at least one unit aged over 90 days, and a better return available from acting (such as lowering the price) as the signs it uses for excess inventory.

It is a surcharge, so it comes on top of the regular monthly storage fee for those units, not instead of it.

Far more cover than your reorder math calls for is often a pricing problem, not a buying one. In the lesson, Stef sorts his products by days of inventory and treats anything over about 60 days as a sign the price is not winning enough sales, so he looks at the price first (Restocking, from about 10:46).

Why Amazon's restock report may disagree with you

Seller Central has its own restock tool. In the same Seller Forums post on FBA inventory tools, Amazon staff describe the Restock Inventory page as showing days of supply, a recommended ship quantity and a recommended ship date for each product, with recommendations "based on your sales history, seasonality, and demand forecasts." You can adjust supplier lead times, case pack quantities and reorder frequency, and Amazon's tip reads: "Accurate lead times and reorder frequencies in Restock Inventory lead to better recommendations."

When Amazon added restock suggestions to Send to Amazon, its announcement was just as clear about their limits: "These recommendations are a guide only and shouldn't be used as a substitute for your own judgement."

So if Amazon's number is far from yours, don't pick one at random. Find the input that differs:

• Settings you never filled in. If you have not entered a lead time for the product, Amazon is not using yours. It can't know that your supplier takes 12 days and your prep center 3.
• Reorder frequency. It is one of the tool's inputs, and a quantity meant to last until your next shipment grows with the gap between shipments. If the setting doesn't match how often you actually send stock, the quantity won't either.
• A forecast against an average. Amazon's suggestion uses seasonality and demand forecasts; your reorder point uses your recent pace. Before a busy season Amazon may ask for more than your average suggests, and after a one-off spike your own average may be the one running high.
• Stock it can't see. Units at your prep center and open orders with your supplier are invisible to Amazon until they become a shipment.
• Things neither of you can see yet. A new seller on the listing, a price drop or a competitor running out will change your sales after both numbers were worked out.

If so, a product whose sales changed over the last month can get a suggestion that lags behind what you see now.

Do your own math first, then put Amazon's number beside it. If Amazon wants several times what your pace and lead time suggest, check its lead time and reorder frequency settings, then whether it is forecasting a season you are not. If it wants less, check whether you are counting stock that Amazon is not.

Doing this for every product

The math on this page takes a minute for one product. Across a few hundred products from several suppliers, it becomes a spreadsheet you rebuild every week.

That is the job of Apex Blue. It syncs your FBA inventory and sales from Amazon every few minutes. You enter each supplier's lead time once, add prep days and choose the days of cover you want, and it shows days of stock left and a restock status for each product. The products you pick become a purchase order grouped by supplier, with your recorded costs and case packs. Its suggestions are arithmetic on your stock, sales pace and settings, not a demand forecast, so you can check any of them with the formulas on this page.

See how inventory and restock planning works in Apex, the Apex Blue overview or how a reorder moves through the purchase order workflow. Stef walks through the whole restock routine in the lesson below. Some Apex screens in it may look different today. As the catalog grows, more of your buying becomes restocks like these, which our guide to what changes as a wholesale business grows covers.