Depths are in inches (product units). The server converts to millimetres for the LPS SWMM model. Display units on this page do not change the INP.
Honeycomb is described as porosity in product terms. In SWMM, the detention layer uses a STORAGE row with void ratio, not porosity.
This tool only adjusts thickness in SWMM; void ratio stays at the model default (0.98).
Storage thickness sent to SWMM is 2 × (honeycomb + 0.2″) (product convention for how SWMM treats storage).