How Can a Trader Calculate the “Realized Slippage” after a Trade Is Executed?

Realized slippage is calculated by taking the difference between the price at which the order was submitted (or the mid-price at the time of submission) and the final price at which the order was actually executed. For a buy order, realized slippage is the execution price minus the reference price; for a sell order, it is the reference price minus the execution price.

A positive number indicates the cost of slippage, while a negative number indicates price improvement.