Measuring your seat hight helps you compare different seats and systems.

How to measure seat height.

Place a straight edge across the coaming above the seat and measure down into the lowest part of the seat bowl, along the centre line.

Remove the seat and measure to the hull.

Subtract one measurement from the other and you have the seat height including any foam and material thickness. You can now compare seats between similar hulled boats.
Boats vary in draft (depth in the water) this can be as much as 35mm between flatter and narrower hull sections. Your seat height and stability are relevant to the water level.