Degree of Unsaturation (DBE) Calculator
Enter a chemical formula to find its degree of unsaturation (rings + π bonds). Supports parentheses, nesting, hydrates (·), halogens, and optional charge.
Background
The degree of unsaturation (also called DBE) equals the total number of rings + π bonds
in a formula unit. For most general chemistry/organic problems, use:
DBE = (2C + 2 + N − H − X + q) / 2
where X = halogens (F, Cl, Br, I), and q is the net charge
(e.g., +1 for cations, −1 for anions). Oxygen/sulfur/selenium/tellurium are ignored.
How to use the calculator
1) Enter a valid chemical formula (case-sensitive element symbols, supports parentheses and hydrates).
2) Optionally enter net charge (e.g., +1 or −1). Leave blank for neutral.
3) Click Calculate DBE to see DBE and a full element breakdown.
Interpreting the result
- DBE = 0 → fully saturated (no rings/π bonds).
- Each ring adds 1; each double bond adds 1; each triple bond adds 2.
- Aromatic benzene ring contributes DBE = 4 (one ring + three π bonds).
Formula & Equation Used
DBE = (2C + 2 + N − H − X + q) / 2
- C = number of carbons; H = hydrogens; N = nitrogens; X = halogens (F, Cl, Br, I).
- q = net charge: +1 for cations, −1 for anions (0 if neutral).
- Chalcogens like O, S, Se, Te are ignored in the formula.
Example Problems & Step-by-Step Solutions
Example 1
C6H6 (benzene): C=6, H=6, N=0, X=0, q=0
- DBE = (2·6 + 2 + 0 − 6 − 0 + 0) / 2 = (12 + 2 − 6)/2 = 8/2 = 4.
- Interpretation: one ring + three double bonds.
Example 2
C5H5N (pyridine): C=5, H=5, N=1, X=0, q=0
- DBE = (2·5 + 2 + 1 − 5 − 0 + 0) / 2 = (10 + 2 + 1 − 5) / 2 = 8 / 2 = 4.
Example 3 (ion)
NO2−: C=0, H=0, N=1, X=0, q=−1
- DBE = (0 + 2 + 1 − 0 − 0 − 1) / 2 = 2 / 2 = 1.
Frequently Asked Questions
Q: Do oxygen and sulfur affect DBE?
No. Chalcogens (O, S, Se, Te) are ignored in the DBE formula.
Q: How do halogens count?
Halogens (F, Cl, Br, I) count like hydrogen: subtract them in the (H + X) term.
Q: What about charge?
Use q = +1 for cations, −1 for anions. This makes DBE come out integral for ions.
