The Viscosity Compensation Factor (V-Factor) was developed for use with single-orifice restrictors. If you know your V- Factor when using the Lohm Calculator, you can check the box and manually enter the value. Otherwise, this calculator will compute it for you. Since V-Factor is an approximation for single orifice restrictions, its accuracy diminishes when applied to other geometries, with accuracy further diminished in applications where fluid viscosity is greatly increased. It should therefore only be used as a general guide if the resistance flow path is anything other than a single orifice.