The molecular formula of cholesterol is C₂₇ H₄₅ OH. It is monounsaturated tetracyclic alcohol. The structure of cholesterol, as proposed by Windaus, has the following characteristic features:

1. Cyclopentanoperhydrophenanthrene ring system
2. An aliphatic side chain attached to C₁₇
3. An OH group attached to C₃
4. A double bond between C₅ and C₆
5. Two methyl groups; one attached at C₁₀ and other at C₁₃