Degree of Unsaturation Calculator
Use our degree of unsaturation calculator to calculate DoU (also called IHD) from a molecular formula. Enter carbon (C), hydrogen (H), nitrogen (N), and halogens (X) to get the degree of unsaturation. Includes the DoU formula, examples, and what degrees of unsaturation tell you.
What Is Degree of Unsaturation?
Degree of unsaturation (DoU), also called index of hydrogen deficiency (IHD), tells you how many rings and pi bonds are present in a molecule based on its molecular formula.
Each degree of unsaturation corresponds to one ring or one double bond equivalent. A triple bond counts as two degrees of unsaturation because it contains two pi bonds.
Chemists use degrees of unsaturation to narrow down possible structures when interpreting molecular formulas, mass spectrometry, and NMR data.
Degree of Unsaturation Formula
This calculator uses the standard DoU (IHD) equation for formulas containing C, H, N, and halogens (X). Oxygen and sulfur do not affect the calculation and are omitted from the equation.
C = carbons, H = hydrogens, N = nitrogens, X = halogens (F, Cl, Br, I).
Benzene has 4 degrees of unsaturation (one ring + three double bonds).
A DoU of 0 suggests no rings or multiple bonds (fully saturated).
How to Calculate Degree of Unsaturation
- 1
Enter the number of carbon atoms (C).
- 2
Enter the number of hydrogen atoms (H).
- 3
Enter the number of nitrogen atoms (N).
- 4
Enter the number of halogen atoms (X).
Frequently Asked Questions
It means the molecule has one ring or one double bond equivalent. For example, one double bond adds 1 DoU, and one ring adds 1 DoU.
They tell you the total number of rings and pi bonds in the structure. DoU does not tell you exactly where they are, only how many are present in total.
Benzene (C6H6) has DoU = 4.
Halogens behave like hydrogen in terms of valence in many organic formulas. Each halogen replaces one hydrogen, so they are counted in the same subtraction term.
Many students use quick references like: ring = 1, double bond = 1, triple bond = 2. A DoU value is the total of these components in any valid structure.