Provide coil geometry and inductance will be estimated. Relative Permeability and Wire Diameter are optional.
The "Square Cross-Section" value is for a coil wound on a square form instead of the cylinder, the Diameter in this case is the side-length (across the flats). Wire thickness should be taken into account for best accuracy, the Diameter to be specified is the mean diameter of the current flow. The "Long Solenoid" value is for a solenoid without flux leakage due to finite length, you can consider this an upper-bound on the inductance you will achieve with a circular coil. Square coils can exceed this value because of their larger cross-sectional area. The formulas are based on circular wire and have limitations on the "aspect ratio" of coils for which they will be accurate. If you provide a wire diameter a figure taking it into account will also be computed.