Molecular descriptor is a result of standardized numerical calculation from logical and mathematical interpretation of chemical information, such as chemical formula, molecular structure, interaction and etc., from a molecule. [Roberto Todeschini and Viviana Consonni, “Handbook of Molecular Descriptors”, Wiley-VCH, 2000] In this section, the methods and definitions of calculating molecular descriptors are introduced. PreADMET supports 2D molecular descriptors and/or 3D molecular descriptors due to its input.

Theoretical molecular descriptor are categorized into the following categories.

Constitutional descriptors
	No. of atoms, No. of bonds, Molecular weight, the number of rotatable bonds, the number of H bond acceptors/donors etc.
Topological descriptors
	wiener index, connectivity indices, valence connectiviry indices, kappa shape indices, kappa alpha indices, balaban indices etc.
Lipophilic descriptors
	Ocatanol-water partition coefficient (ClogP, AlogP, XlogP etc.), logD etc.
Geometrical descriptors
	moments of inertia distance relateddescriptors surface area relateddescriptors (polar surface area, van der Waals surface area etc.) volume relateddescriptors etc. (van der Waals volume, solvent accessible volume etc.)
Electronic descriptors
	partial charge(Zefirov, Delphi, Gasteiger-Marsili method), palarity parameter, Apol(sum of atomic polarizabilities), dipole moment, HOMO, LUMO etc.
Thermodynamic descriptors
	Hf(Heat of formation), molar refractivity etc.
Otherdescriptors
	conformational descriptors, quantum chemical descriptors, receptor descriptors, molecular field analysis(MFA) descriptors, receptor surface analysis(RSA) descriptors, molecular shape analysis(MSA) descriptors etc.