Cart abandonment rate is an online shopping metric that shows the rate of potential customers who leave a site before completing their purchases compared to all the shopping carts created. Learn how to improve yours here. Here’s how to calculate cart abandonment rate in two steps: Step 1: [Completed Purchases] /[ Shop Carts Created x 100] = Percentage of Successful Transactions. Step 2: [100] – [Percentage of Successful Transactions] = Cart Abandonment Rate