Amazon Restock Limits: A Calculator to Avoid December Stockouts
Amazon restock limits get tighter in Q4 while inbound shipments get slower, so the reorder that saves December has to leave weeks earlier than your gut says. Here's the date math, the capacity check, and a free calculator that finds your reorder-by date.
Your restock limit is a forecast. Somebody else's forecast, about your product, turned into cubic feet.
Here's the short answer. Amazon restock limits now work as one monthly FBA capacity limit, measured in cubic feet, and it counts the stock you already have at Amazon plus every shipment you've created that hasn't arrived. Amazon's own holiday 2026 post warns you "may see lower capacity limits" in peak season, because its buildings focus on receiving in September and October and on shipping orders in November and December. Less space, slower check-in. So the reorder that protects December has to leave in early to mid November.
For the hypothetical ASIN in this post, the reorder-by date is November 11. Miss it and the listing goes dark on December 13, twelve days before Christmas.
The rest of this post is the math behind that date, the capacity check most sellers skip, and a free calculator that does both for your own numbers.
What are Amazon restock limits in 2026, really?
The name stuck around longer than the system did.
In January 2023 Amazon announced that from March 1, 2023 it would replace weekly restock limits and storage limits with "a single monthly limit" that decides how much inventory you can send to and store at Amazon. Sellers still call it the restock limit. Seller Central calls it your FBA capacity limit. Same thing.
Here's what I could confirm from Amazon's own pages this week, and what I couldn't.
| Rule | What Amazon says | Source |
|---|---|---|
| One monthly limit | Replaced weekly restock limits and storage limits from March 1, 2023 | Amazon announcement |
| Measured in cubic feet | Units are shown as an estimate only | Same |
| What counts as usage | Inventory on hand plus shipments you've created that haven't arrived | Amazon forum post |
| When next month's limit appears | Third full week of each month, in the Capacity Monitor plus an email | Same |
| How far ahead you can see | Confirmed limit for next month, estimates for the two months after | Same |
| What shapes your limit | IPI score, ASIN sales forecasts, shipment lead time, fulfillment center capacity | Amazon announcement |
| Extra factors named by Amazon staff | Sales history, seasonal periods, scheduled deals | Amazon staff reply |
| New professional accounts | No capacity limits for the first 39 weeks in FBA | Amazon refresher |
| Individual accounts | Fixed at 15 cubic feet, can't be raised | Same |
| Peak season 2026 | "You may see lower capacity limits during this time" | Amazon holiday 2026 post |
Now the honest part. Seller Central help pages sit behind a login, so I worked from Amazon's public announcement and posts by Amazon staff and News_Amazon on the Seller Forums. Three things you'll read elsewhere I could not confirm on an Amazon page:
- The 2025 cut. AMZ Prep says Amazon cut capacity by up to 75% in May 2025 and moved the formula from 6 months to 5 months of projected sales. They don't link Amazon for either number.
- ASIN-level caps. Seller Labs reports Amazon brought back per-ASIN restock caps in April 2025, with many sellers seeing limits tied to about 90 days of supply, and says there was no official announcement.
- Overage fees. Amazon's 2023 rules charged overage fees on on-hand stock above your limit. SupplyKick says those fees were dropped in July 2024, while the shipment block stayed.
So treat the table as the floor, and your own Capacity Monitor as the truth. It's at the bottom of the FBA dashboard.
Your restock limit is Amazon's forecast of your sales, converted into space, and it gets less generous right when you need it most.
Why do December stockouts start in October?
Because two clocks run at once, and both get slower in Q4.
Clock one is your limit. Amazon sets it from forecasts, IPI and how much room its buildings have. In peak season the buildings are full of everybody's Black Friday stock, and Amazon has already told you to expect less space.
Clock two is your lead time. That's every day between deciding to reorder and the units being sellable: supplier or 3PL prep, freight, and Amazon receiving. The receiving piece is the one that stretches. Amazon's own holiday post says its fulfillment centers focus on receiving in September and October and on customer orders in November and December. So a pallet that pulls up to the dock in late November is arriving when the building is set up to ship, not receive. I plan for slower check-in then. That's my assumption, not an Amazon number, and you should replace it with your own receiving history from last November.
Put the two together and you get the trap. You look at your stock in October, it looks fine, and you wait. By the time it looks thin, the limit is tight and the lead time is long.
Here's the thing. Most sellers check days of cover by dividing what they have by what they sold last week. In October that number lies to you.
How do you calculate days of cover the right way?
Run the math on a seller like this, a hypothetical. One ASIN. Today, October 23, there are 2,400 units sellable at Amazon. The Black Friday stock already landed. The question is December.
Normal October velocity is 30 units a day. So the quick math says 2,400 divided by 30 is 80 days of cover. That's into January. Relax, right?
Wrong. Here's the forecast for the rest of the year, built from last year's pattern. These multipliers are assumptions. Use your own from last Q4.
| Window | Days | Units per day | Units sold |
|---|---|---|---|
| October 23 to 31 | 9 | 30 | 270 |
| November 1 to 19 | 19 | 35 | 665 |
| November 20 to 30 (Black Friday Week and Cyber Monday) | 11 | 75 | 825 |
| December 1 to 20 | 20 | 50 | 1,000 |
| December 21 to 31 | 11 | 25 | 275 |
| Total, October 23 to December 31 | 70 | 3,035 |
Now walk the stock forward.
- Start: 2,400 units.
- After October: 2,400 minus 270 is 2,130 on November 1.
- After the quiet part of November: 2,130 minus 665 is 1,465 on November 20.
- After Black Friday Week and Cyber Monday: 1,465 minus 825 is 640 on December 1.
- December at 50 a day: 640 divided by 50 is 12.8 days.
The listing runs out on December 13. Not January. December 13.
Counting from today, the stock really lasts 51 days. By October 25, the first week in the chart below, that's down to 49. Here's how it drains, week by week, if you never reorder.
Days the stock on hand lasts at forecast demand: 30 a day in October, 35 in early November, 75 for Black Friday Week, 50 to December 20, 25 after.
Look at the shape. A steady slide, a week per week, and then a cliff. Nothing in October tells you there's a problem, because 42 days of cover on November 1 looks healthy. It isn't, once Black Friday Week eats 825 units in 11 days.
Days of cover based on last week's sales is a rear-view mirror. In Q4 you have to drive with the windshield: forecast demand, week by week.
How do you find your Amazon reorder-by date?
Here's the method. Five steps, and every one of them is plain arithmetic.
- Forecast daily demand by week through December 31.
- Set a safety stock in days of December demand.
- Find the date your stock falls to that safety level.
- Add up your real Q4 lead time: prep, freight, receiving.
- Subtract the lead time from the safety date. That's your reorder-by date.
Now run it on the same hypothetical ASIN.
Safety stock. I like 10 days of December demand for a product with a long, lumpy lead time. 10 days at 50 a day is 500 units.
Safety date. Stock is 640 on December 1, then 590, then 540 at the start of December 3. During December 3 it drops under 500. So the reorder has to be sellable by December 3.
Lead time. Here's where Q4 bites. Same seller, same 3PL, two different seasons. Hypothetical numbers again.
| Lead time step | Normal month | Q4 (late November arrival) |
|---|---|---|
| 3PL prep, labeling, pickup | 3 days | 5 days |
| Freight to the fulfillment center | 6 days | 8 days |
| Amazon receiving until sellable | 3 days | 9 days |
| Total lead time | 12 days | 22 days |
Reorder-by date. December 3 minus 22 days is November 11. With a normal 12-day lead time it would have been November 21.
Ten days. That's what Q4 steals. And most sellers lose it without noticing, because their gut still runs on the 12-day number from June.
How many units should you send for December?
Enough to get through December 31 and still hold your safety stock into January. Not one carton more, because December storage is the most expensive rent of the year.
The formula:
Order quantity = demand from arrival to December 31 + ending safety stock minus stock on hand at arrival
Same hypothetical ASIN:
- Demand from December 3 to 20: 18 days at 50 is 900 units.
- Demand from December 21 to 31: 11 days at 25 is 275 units.
- Total demand from arrival: 1,175 units.
- Ending safety stock: 10 days of January demand at 30 a day is 300 units.
- Stock on hand when the shipment lands (start of December 3): 540 units.
- Order quantity: 1,175 plus 300 minus 540 is 935 units.
Check it by walking forward. 540 plus 935 is 1,475 on December 3. Minus 1,175 through December 31 leaves 300 on January 1. Ten days of January cover. Clean.
Here's the same chart with the reorder in it.
Same forecast as the first chart. The reorder ships November 11 with a 22-day Q4 lead time and is sellable December 3.
The low point is 14 days on November 29, right after Black Friday Week. That's a little thin, and I'll come back to why in a minute. But nothing hits zero, and you walk into January with 300 units instead of a dead listing.
Will your FBA capacity limit even let the shipment through?
This is the step almost every restock calculator skips. You can have the perfect date and the perfect quantity and still get stopped at the shipment screen.
Remember what counts as usage: stock on hand plus open shipments, in cubic feet. When usage hits your limit, Seller Central won't let you create new FBA shipments until it drops or you buy more room.
So check it before November 11, not on November 11. The formula:
Room = capacity limit minus (cubic feet on hand + cubic feet in open shipments)
Units that fit = room divided by cubic feet per unit
Back to the hypothetical. Each unit is 0.1 cubic feet. The account has a November limit of 450 cubic feet, and the seller's other ASINs use 230 of it.
- On November 11 this ASIN has 1,780 units on hand. 1,780 times 0.1 is 178 cubic feet.
- Total usage: 178 plus 230 is 408 cubic feet.
- Room: 450 minus 408 is 42 cubic feet.
- Units that fit: 42 divided by 0.1 is 420 units.
The plan needs 935. Only 420 fit.
That's the moment sellers panic and do one of two bad things. They send 420 and hope. Or they wait for the December limit and ship everything on December 1, which, with a 22-day lead time, lands on December 23. Both of those end in a stockout.
The reorder date tells you when. The capacity check tells you if. Run the second one before you fall in love with the first.
What can you do when the capacity limit blocks your reorder?
You've got four levers. Here's how I'd rank them for a December rescue, best first.
1. Split the shipment around Black Friday Week. Send what fits now and the rest once usage drops. In the hypothetical, the 420 units ship November 11 and are sellable December 3. Then Black Friday Week does you a favor: it burns through stock. By November 22 this ASIN is down to 1,315 units, which is 131.5 cubic feet. Say the other ASINs have sold down to 215 cubic feet. Add the 42 cubic feet already in the open shipment and usage is 131.5 plus 215 plus 42, which is 388.5. Room is 450 minus 388.5, which is 61.5 cubic feet, or 615 units. The other 515 units fit. They ship November 22 and are sellable December 14.
Check the math. Stock is 540 plus 420, or 960, on December 3. Eleven days at 50 takes it to 410 on December 14. Add 515 and it's 925. December 14 to 20 is 7 days at 50, which is 350. December 21 to 31 is 275. 925 minus 625 is 300 on January 1. Same ending as the single shipment. The lowest point is 10 days of cover on December 13, the day before the second shipment lands. Tight, but never dark.
2. Clear space you're wasting. Slow stock on other ASINs eats the same cubic feet your winner needs. An Amazon rep's advice, as quoted by Seller Labs, was to address "excess or unhealthy inventory to free up more capacity for faster-selling products." Do it now, not in November. If you're not sure which ASINs are dead weight, start with finding slow-moving inventory before your Q4 buy. And look at what that dead stock costs to keep in the aged inventory surcharge breakdown.
3. Bid in Capacity Manager. Amazon lets you request extra space with a reservation fee you choose. In its announcement, Amazon says requests are granted "starting with the highest reservation fee per cubic foot," and performance credits "are designed to offset up to 100% of the reservation fee" when the extra space turns into sales. An Amazon refresher post says requests are checked "typically twice per week." There's no guarantee, and peak weeks are when everyone bids. Before you bid, divide the fee by the profit those extra units will earn. beBOLD Digital makes the same point: confirm the margin on the extra units covers the fee.
4. Stage stock in AWD. Amazon's holiday 2026 post says sellers who enrolled in Amazon Warehousing and Distribution in Q4 2025 reported more than 13% more shipped units and more than 30% fewer out-of-stock days. That's Amazon reporting on its own program, so weigh it that way. Several publishers, including AMZ Prep, say AWD stock doesn't count against your FBA limit. I couldn't confirm that on an Amazon page. If you go this route in late October, check how your Capacity Monitor treats it before you count on the space.
Here's all four side by side.
| Lever | Speed | Cost | Risk |
|---|---|---|---|
| Split shipment | Fast, uses space you'll have anyway | Two inbound shipments instead of one | Second shipment lands later, so your safety stock runs thinner |
| Clear slow stock | Slow in Q4, removals take time | Removal or liquidation fees, lost margin on the cleared units | Starts too late if you wait until November |
| Capacity Manager bid | Depends on demand for space | Reservation fee, partly offset by performance credits | Not guaranteed, peak weeks are crowded |
| AWD staging | Slowest to set up | AWD storage and transfer costs | Rules on capacity treatment I couldn't verify |
What does a December stockout actually cost you?
More than the units. But start with the units, because that part is plain math.
Back to the no-reorder version of the hypothetical. On December 13 there are 40 units left. Demand from December 13 to 20 is 8 days at 50, which is 400. Demand from December 21 to 31 is 275. That's 675 units of demand against 40 units of stock, so 635 orders you can't fill.
At a hypothetical $34.95 price, 635 times $34.95 is $22,193.25 of revenue gone in the last 19 days of the year.
Then there's the part I can't put a clean number on. When an FBA listing goes out of stock, the ad campaigns behind it stop serving, the sales history that props up your ranking takes a hit, and a competitor collects the December buyers who searched for you. I've watched sellers spend most of January buying back the position they had on December 12. That's my experience, not a published stat. I'd still plan as if it's true.
A stockout costs you the sales you missed, then hands your ranking to whoever had stock that week.
The opposite mistake costs money too. Say the seller panics and sends 2,000 units instead of 935. That's 1,065 extra units, or 106.5 extra cubic feet. AMZ Prep reports standard-size storage at $2.40 per cubic foot a month from October to December. 106.5 times $2.40 is $255.60 for December alone, and those units keep paying rent into the new year. Leave them long enough and they drift toward the aged inventory surcharge.
So there are two ways to lose. Short and you bleed sales. Long and you bleed storage. The calculator's job is to land you between them.
There's a third trap on the short side. Run a variant too thin and Amazon can charge the low inventory level fee on every unit you do ship. Cutting it close in December can cost you twice.
How should you set safety stock for Q4?
Safety stock is the cushion for the two things you can't control: demand you didn't forecast and freight that runs late. In Q4 you get more of both.
Here's how I'd think about it.
- Measure it in days, then convert to units. 10 days of December demand at 50 a day is 500 units. If December runs at 80 a day, the same 10 days is 800 units. Days scale with your forecast. Fixed unit counts don't.
- Size it to your worst lead time. If your last Q4 shipment took 9 days to check in, and a normal one takes 3, that 6-day gap is your minimum cushion.
- Watch the post-Black Friday dip. In the reorder chart, cover drops to 14 days on November 29. That's the week Black Friday Week demand meets a shipment that hasn't landed yet. If your Black Friday lift could be bigger than you forecast, move the reorder earlier by a few days, not the quantity higher.
- Don't let safety stock become January dead stock. 300 units is 10 days of January at 30 a day. That's a cushion. 1,300 units would be a storage bill.
One more thing. Your ending safety stock is your next lead time. If your January reorder takes 12 days door to sellable, 10 days of cover on January 1 means you're already behind. In that case, reorder for January in the same November window. Yes, it's early. Q4 makes everything early.
How is AI changing Amazon restock planning?
Amazon is already planning your stock with a forecast, whether you like it or not.
Its announcement says capacity limits come from your IPI score, "sales forecasts for their ASINs," shipment lead time and fulfillment center capacity. An Amazon staff reply adds seasonal periods and scheduled deals. That's a model. It looks at your history, guesses your future and hands you a number of cubic feet. beBOLD Digital, citing Nova Analytics, describes it as five signals: sales velocity, forecasted demand, IPI, fulfillment center capacity and network movement speed.
So here's my take. You're not going to out-negotiate that model. You can only out-forecast it.
The seller who walks into November with their own week-by-week forecast, their own Q4 lead time and their own capacity check knows their reorder date before Amazon's limit lands. The seller running on last week's sales finds out from the shipment screen.
The good news is that the forecast doesn't need to be clever. The table in this post is five rows. The hard part is doing it in October instead of December.
The other thing I'd steal from the way Amazon runs this: the 14 to 21 day rolling cadence. beBOLD suggests moving from 90-day bulk inbounds to 14 to 21 day rolling replenishment. In Q4 that rhythm is what makes a split shipment feel normal instead of like an emergency.
Why does every restock problem trace back to the same landlord?
Look at every rule in this post. The limit. The lead time. The receiving week. The overage policy. The reservation fee. Amazon sets all of it, and changes it when it needs the space.
I'm not telling you to leave Amazon. I sold on it. It's the biggest shelf on earth. I'm telling you that if the only shelf you own stock on can shrink in your biggest month, you're one forecast away from a dark December.
So I always ask sellers the same question in Q4: what would your best Amazon product earn on a page you control?
Three client products on our results page answer that. Real client numbers, not typical results, and not a promise of what your store will do. One animal repellent made $3.83 net profit per sale on Amazon at a $17.95 price. On Shopify, at a $24.95 price with a 3% platform fee instead of 15%, and a $101.38 average order value, it made $48.27 net profit per sale, after paying for ads and inventory.
Now revenue per visitor. It's conversion rate times average order value. Run the math on a store like this, a hypothetical: 10,000 visitors in December, a 1.5% conversion rate and a $60 average order value. That's $0.90 per visitor, or $9,000 for the month. Rebuild the product page so it converts at 2.5% with a $96 average order value, and the same 10,000 visitors are worth $2.40 each, or $24,000. No capacity limit on that one.
If you want the side-by-side, Shopify vs Amazon revenue per visitor in 2026 lays it out. If you want to keep Amazon doing the fulfillment for both, the Multi-Channel Fulfillment fee math for Shopify shows when that pays. And our Amazon seller page explains why sellers move their winners.
Amazon decides how many units you're allowed to sell in December. Your own store doesn't ask.
Where does this fit in your Q4 plan?
This post is the December piece. The rest of the season lives in a few other places.
- The Black Friday arrival cutoffs and the backward plan are in the Amazon Q4 2026 deadlines. If you're reading this on October 23, the October 28 cutoff for Amazon-optimized splits is five days out.
- The peak fees that start October 15, and what they add per unit, are in the Amazon FBA fee changes for 2026.
- The day-by-day operating plan for the season is in the Amazon Q4 strategy playbook.
- And the full map of selling on Amazon this year starts with the Amazon selling guide for 2026.
What to do next
One move, today. Open the Capacity Monitor at the bottom of your FBA dashboard and write down your November limit and your current usage. Then take your top three ASINs, forecast December week by week, and find the date each one falls to 10 days of cover. Subtract your real Q4 lead time. If any date lands before November 15, start the shipment plan this week, and check it against the room you actually have before you build the boxes.
Book Your Profit Audit
Amazon restock limits decide how much of your best product you're allowed to sell in December, and the limit shrinks right when buyers show up. The profit audit shows you what that product would earn on a store you control, then we rebuild a high-converting product sales page in less than 15 minutes.
Or go here to check it out → revenueflows.ai
P.S. Amazon's limit is a forecast of your sales. Beat it with your own forecast in October, then build the shelf nobody can shrink.
Frequently asked questions
What are Amazon restock limits?
Restock limits are the caps on how much inventory you can send to and keep in Amazon's fulfillment centers. Since March 2023 Amazon has run them as one monthly FBA capacity limit, measured in cubic feet, and it counts both the units on hand and the shipments you've created that haven't arrived yet.
How does Amazon calculate FBA capacity limits?
Amazon says limits are shaped by your Inventory Performance Index score, the sales forecasts for your ASINs, shipment lead time, seasonal periods, scheduled deals and how much space its fulfillment centers have. In practice your limit is Amazon's forecast of what you'll sell, turned into cubic feet.
When does Amazon announce next month's capacity limit?
Amazon's announcement says next month's limit is posted in the third full week of each month in the Capacity Monitor, at the bottom of the FBA dashboard, with an email. It also shows estimates for the two months after that, which can move up or down.
What happens if I go over my FBA capacity limit?
Seller Central stops letting you create new FBA shipments until your usage drops back under the limit or you win extra space through Capacity Manager. Amazon's 2023 rules also charged overage fees on on-hand inventory above the limit, and SupplyKick reports those fees were dropped in July 2024.
How do I calculate my Amazon restock date for December?
Project your daily sales week by week through December, find the day your stock falls to your safety level, then subtract your full Q4 lead time: prep, freight and Amazon receiving. That's your reorder-by date. For most sellers it lands in early to mid November, not December.
Does AWD inventory count against FBA capacity limits?
Several seller-tool publishers, including AMZ Prep, say inventory stored in Amazon Warehousing and Distribution doesn't count against your FBA capacity limit. I couldn't confirm that on an Amazon page, so check your own Capacity Monitor before you plan around it.