[ ESP = (SP_supply + SP_return) - (PD_filter + PD_coil + PD_grille + PD_elbow) ]
In most field scenarios, technicians use a simplified version: esp calculation hvac excel sheet
TESP (Total External Static Pressure) includes everything outside the fan housing. In practice, ESP = TESP. [ ESP = (SP_supply + SP_return) - (PD_filter