Note on measurements / waistband: "Width" of the waistband when the boardshorts are laid flat. So for comparison, measure the "width" at the waistband of your trousers and compare it with the values in the table. Measurements in cm.
Reference size: For a body height of 1.78 m with a regular "jeans size" of 32/32, a size L is worn. There is still plenty of room for flexibility, for example, to also fit a 34 or 36, since the waistband is flexible.