Because slippage is unavoidable it is something you need to account for in your trading plan. Slippage will figure into your final trading costs, alongside other costs such as spreads, fees, and commissions. One way to do this is to look at the slippage you've experienced over the course of a month or longer and use the average slippage when computing your trading costs. This will give you a more accurate representation of how much you need to make to record a profit.