TRIM CALCULATOR Required Variables Top Trim: Bottom Trim: Average Trim: Number of Stages: Answer Area Notes/Instructions Top Trim = Full Trim Impeller on the pump curve. Bottom Trim = Lowest Trim allowed on the pump curve. Average Trim = Recommended trim of all impellers to meet your design point Number of Stages = Numbers of stages/impellers of the selection. This calculator will allow you to use as many full impellers as possible. Below is a video link showing how to use the calculator.