What is a good sales velocity window for Amazon FBA?

There is no single right window. A trailing 7 to 14 day window reacts quickly to changes and suits trending or seasonal SKUs; a 30 to 90 day window is steadier and suits stable products. Many sellers watch both and weight the recent window when the two diverge.

How does sales velocity affect restock?

Velocity is the multiplier in every restock formula. Reorder point is velocity times lead time plus safety stock, and reorder quantity is velocity times the days you need to cover. If your velocity number is wrong or stale, every downstream restock number is wrong too.

December 8, 20257 min readInventory Planning

Sales Velocity: How to Calculate and Use It on FBA

Sales velocity is units sold per day, the engine of every restock decision. How to calculate it, why the window matters, and how to use it on Amazon FBA.

T. Brian Jones

Co-founder & CTO, Inventory Hero

Frequently Asked Questions

How do you calculate sales velocity?: Divide units sold by the number of days in the period. If you sold 360 units in 30 days, your sales velocity is 12 units per day. Calculate it per SKU, not as a blended account average, because the account number hides your slow and fast movers.
What is a good sales velocity window for Amazon FBA?: There is no single right window. A trailing 7 to 14 day window reacts quickly to changes and suits trending or seasonal SKUs; a 30 to 90 day window is steadier and suits stable products. Many sellers watch both and weight the recent window when the two diverge.
How does sales velocity affect restock?: Velocity is the multiplier in every restock formula. Reorder point is velocity times lead time plus safety stock, and reorder quantity is velocity times the days you need to cover. If your velocity number is wrong or stale, every downstream restock number is wrong too.

Written by

T. Brian Jones

Co-founder & CTO, Inventory Hero

T. Brian Jones is co-founder and CTO of Inventory Hero. He leads the engineering behind its Amazon data pipeline, demand forecasting, and the AI platform that lets sellers talk to their live inventory, sales, and supplier data in plain language.

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How do you calculate sales velocity?

Divide units sold by the number of days in the period:

Sales velocity = units sold / days in period

If a SKU sold 360 units over the last 30 days, its sales velocity is 360 / 30 = 12 units per day. Pull the units-sold history from your Seller Central Business Reports (by ASIN, over a date range). Always calculate it per SKU. A blended account-level velocity averages your winners and your slow movers together and hides exactly the SKUs you most need to watch. See the sales velocity definition for the short form.

One adjustment matters more than any other on FBA: if the SKU was out of stock for part of the window, exclude those days from the denominator. A SKU that sold 360 units in the 22 days it was actually in stock has a velocity of about 16 per day, not 12. Divide by the full 30 and you understate demand, which then sets your reorder point too low and walks you straight into the next stockout.

Why the averaging window changes the answer

The same SKU has different velocities depending on how far back you look, and that choice matters more than sellers expect.

A short window (7 to 14 days) reacts fast. It catches a SKU that is heating up or cooling off quickly, which is what you want for trending or seasonal products. The cost is noise: a single good or bad week swings it.

A long window (30 to 90 days) is steady and smooths out noise, which suits stable, predictable SKUs. The cost is lag: it is slow to notice a real change in demand.

A practical approach is to watch both and weight the recent window when the two diverge, because a divergence usually means the SKU is changing.

Use the trend, not just the average

The most expensive velocity mistake is planning to a blended average while demand is moving. A SKU climbing from 12 to 20 units a day still shows a 30-day average somewhere in the middle, and if you plan to that middle number you under-order and stock out partway up the climb.

Window	Units sold	Days	Velocity
Last 7 days	140	7	20/day
Last 30 days	480	30	16/day

Window

Units sold

Days

Velocity

Last 7 days

140

20/day

Last 30 days

480

16/day

The 30-day average says 16, but the recent week says 20 and rising. Plan the reorder on 16 and you are already behind. The trend is the signal; plan to where velocity is heading, not where it has been. Run the downstream numbers in the reorder point calculator and the sell-through rate calculator.

How velocity drives the rest of the restock plan

Velocity is the multiplier that feeds everything else:

Days of supply = current stock / velocity. It tells you how long until you run out. See days of supply vs days of inventory.

Reorder point = velocity x lead time + safety stock. See when to reorder.

Reorder quantity = velocity x days to cover, plus safety stock. See how to calculate reorder quantity.

Because all three start from velocity, keeping it current per SKU is the highest-leverage thing you can do for restock accuracy. For the full system, see Amazon FBA restock planning.

Sales Velocity: How to Calculate and Use It on FBA

Frequently Asked Questions

T. Brian Jones

Related reading

Demand Planning for Amazon Sellers: A Practical Loop

Amazon Inventory Forecasting: The Complete FBA Guide

AI vs Traditional Inventory Management: Honest Guide

How do you calculate sales velocity?

Why the averaging window changes the answer

Use the trend, not just the average

Worked example

How velocity drives the rest of the restock plan

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