When calculating the profit and loss ratio, many people only calculate how much they make and how much they lose, but forget to take into account spreads, handling fees and slippage. As a result, the theoretical profit and loss ratio is always a bit worse than the actual profit and loss ratio. This article explains how to deduct the cost from the target profit first, recalculate the actual profit-loss ratio according to the post-cost formula, leave cost and slippage buffers for stop loss, test whether the target level is really achieved, and write the estimated cost into the trading plan so that the trading design can withstand the actual test.