Double Bond Equivalent Calculator

Sum of all halogen atoms.
Chemistry

Calculate the Degree of Unsaturation (Double Bond Equivalent, DBE) for an organic molecule from its molecular formula.

Formula

DBE = C − H/2 + N/2 + 1 − X/2
  • Oxygen (O) and sulfur (S) do not appear in the formula.
  • Nitrogen contributes +½ (trivalent); halogens (F, Cl, Br, I) contribute −½.
  • DBE = 4 suggests an aromatic (benzene) ring.
  • Non-integer DBE indicates an error (should always be a whole number or half-integer for radicals).

Benzene (C₆H₆)

Inputs
  • Carbon (C) atoms: 6
  • Hydrogen (H) atoms: 6
  • Nitrogen (N) atoms: 0
  • Oxygen (O) atoms: 0
  • Halogens (F/Cl/Br/I) atoms: 0

DBE = 6 − 6/2 + 0 + 1 = 6 − 3 + 1 = 4 → aromatic ring.

Frequently asked questions

What does DBE = 4 mean?
DBE of 4 suggests an aromatic ring (benzene: 3 double bonds + 1 ring = 4).
Can DBE be a fraction?
For neutral molecules, DBE is always a whole number. Fractions indicate a radical or a formula error.