What is a reorder point?

The inventory level at which you must place a new order to avoid running out. It equals the demand you expect during your supplier lead time plus your safety stock: at 6 sales a day, a 45-day lead time, and 21 days of safety stock, that's (45 + 21) × 6 = 396 units.

Where do I find my average daily sales?

In Seller Central, open Business Reports → Detail Page Sales and Traffic, take units ordered for the last 30 days, and divide by 30. Use the trend slider if that average is clearly rising or falling.

How much safety stock should I carry?

Most FBA sellers carry two to four weeks. Carry more when your supplier's dates wobble, when a single stockout would tank a hard-won ranking, or during Q4; carry less for slow, stable products where storage fees outweigh the risk.

What if my supplier's MOQ is more than I need?

The calculator orders the MOQ and spaces your next orders further apart — a bigger PO simply lasts longer. You'll see it in the cadence: order 504 units at 6 a day and the next PO isn't due for 84 days.

How does it handle growing or declining sales?

The trend you set compounds monthly through every calculation — reorder point, order dates, and quantities. Growth pulls orders earlier and makes them bigger; decline stretches them out, and a steep enough decline shows no reorder needed at all.

Why does it plan three purchase orders instead of one?

Because each order's size determines when the next is due, one date hides the pattern: with a long lead time and short coverage you may need to place PO #2 before PO #1 even arrives. Three dated POs show your reorder rhythm and the cash each one ties up.

FBA Reorder Point Calculator

When to reorder, how many units, and your next three POs

Order next by

On track

—

in 26 days — order 504 units

If you don't order

—

stockout in 92 days

—

Today

550 units on hand

—

PO #1

Order 504 units

—

PO #1 lands

630 units on hand

—

PO #2

Order 504 units

—

PO #3

Order 504 units

Units in FBA

Fulfillable stock right now.

Units inbound

Already shipped to FBA.

Avg daily sales

Your last-30-day average.

6/day

Sales trend

Month-over-month change in demand.

0%/mo

Inventory projection

Projected stock

If you don't order

Reorder point

Safety stock

Why —?

550 units on hand ≈ 92 days of cover

45-day lead time + 21-day safety buffer = order while 396 units (≈ 66 days) remain

92 − 66 ≈ 26 days from today — place PO #1 by —

Your next 3 purchase orders

PO	Place by	Units	Cases	Est. cost	Lands	Stock when it lands
#1	—	504	21	$3,276	—	126safety floor
#2	—	504	21	$3,276	—	126safety floor
#3	—	504	21	$3,276	—	126safety floor

Each PO = 60 days of sales (360 units) raised to your 500-unit MOQ, rounded to 21 case packs of 24.

How the restock math works — and what actually sets your order date

The reorder point
Your reorder point is the stock level that still covers demand across your lead time plus your safety buffer. When fulfillable inventory crosses it, an order placed today lands exactly as you touch safety stock — later than that and you're gambling on the carrier.
Safety stock is time, not units
Thinking in days keeps the buffer honest as sales change: 21 days of safety stock is 126 units at 6 sales a day but 252 at 12. The calculator converts your day setting to units at your current velocity, so the floor moves with demand.
Lead time is door to shelf
Count every day between placing the PO and units becoming fulfillable: production, freight, customs, and Amazon check-in. Sellers who only count the factory quote reorder weeks late — measure your slowest recent order, not your fastest.
Trend changes everything
Growing 20% a month means demand over your lead time is higher than last month's sales suggest — the calculator compounds your trend into every window, pulling order dates earlier as you grow and pushing them out as demand cools.
MOQ and case packs set real quantities
Suppliers sell minimums and full cases, not spreadsheet-perfect quantities. Each planned PO covers your chosen days of demand, gets raised to the MOQ if needed, then rounds up to whole case packs — a number you can actually put on a purchase order.
Three orders ahead
One reorder date tells you what to do this week; three tell you your cash calendar for the next two quarters. Because each PO's size fixes when the next one is due, the calculator plans the chain — so you see overlapping orders coming before they collide.

FBA Reorder Point Calculator

How the restock math works — and what actually sets your order date

Reorder points, safety stock & restock timing