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Average Basket Size

What is Average Basket Size?

Average Basket Size (ABS) is an e-commerce metric that quantifies the composition of transactions by measuring the number of items sold per transaction. In other words, ABS measures the increase or decrease in the quantity of items purchased per transaction.

Alternate names: Items Per Purchase, Average Shopping Cart Size

How to calculate Average Basket Size

ƒ Count(Units in Transactions) / Count(Transactions)


During a particular season, a company had 4,000 transactions and sold a total of 10,000 units. Their ABS for the season is 10,000/4,000 or 2.5.

More about this metric

Average Basket Size is an excellent support metric for Average Order Value (AOV) as it can provide context behind why AOV is either increasing or decreasing.

For example, Corey’s Cyclery has historically held a relatively steady AOV of $250 and an ABS of 2.5 week over week, but as winter arrives and the clearance sales begin, AOV increases to $375. Corey and his team are thrilled with the uptick and begin to review what is driving this increase in AOV. However, in their review they discover that Transactions have remained fixed while Revenue has increased 50%. What is driving this revenue increase?

Reviewing the Average Basket Size, the team is able to see that the 50% increase in AOV was driven entirely by the number of units in customer’s baskets (i.e., +150% increase in ABS from 2.5 to 6.25 units per basket). In other words, the summer clearance encouraged customers to increase the quantity of items purchased in their baskets, but not the number of transactions made.

Continuing to track ABS and using it as a supportive metric will enable Corey’s Cyclery to quickly and easily understand these changes to AOV. Moreover, utilizing ABS in tandem with Average Selling Price (ASP) provides an even greater context to changes in AOV.

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