Degree of Unsaturation Calculator
Convert molecular formula counts into degrees of unsaturation to identify rings and multiple bonds.
Degree of unsaturation
4
Interpretation
Possible rings or multiple bonds: 4
How to Use This Calculator
Gather atomic counts
Obtain the number of C, H, N, and halogen atoms from the molecular formula.
Enter the counts
Fill the fields above. Oxygen and sulfur do not affect the calculation and can be ignored.
Review the result
The output shows the total number of rings plus pi bonds for the structure.
Apply structural reasoning
Use the DU value to constrain potential structures during spectroscopy interpretation.
Formula
DU = (2C + 2 + N - H - X) / 2
DU counts total rings and double bond equivalents. C, H, N, and halogen counts come from the molecular formula.
Example
For C10H14: DU = (20 + 2 - 14) / 2 = 4, indicating four rings, double bonds, or their combination.
Full Description
The degree of unsaturation provides a quick way to infer structural features by comparing the hydrogen count to that of a fully saturated hydrocarbon.
Each double bond or ring reduces the hydrogen count by two, while triple bonds contribute two units of unsaturation. Nitrogen and halogens adjust the hydrogen reference count accordingly.
Frequently Asked Questions
Do oxygen atoms affect the calculation?
No. Oxygen and sulfur do not change the hydrogen reference count and can be ignored for DU purposes.
What does a DU of zero mean?
The structure is fully saturated and acyclic (no rings or pi bonds) under the assumed valence rules.
Can DU be fractional?
Yes for odd counts, but real molecules will have integral combinations of rings and multiple bonds. Fractional results often indicate inconsistent atom counts.
How do halogens enter the formula?
Treat each halogen as if it replaces one hydrogen when calculating DU, so subtract the total halogen count.
Is DU the same as double bond equivalents?
Yes. DU, DBE, and double bond equivalents are interchangeable terms for the same calculation.