Calculate rings-plus-double-bonds (DBE) from a C/H/N/halogen atom count.
| DBE | – |
Use this calculator after you have a formula from MS or combustion and need how many rings and π bonds to draw.
DBE = C + 1 − (H + X − N) / 2. Oxygen and sulfur do not appear. A result of 4 with a benzene-sized C₆ is a classic aromatic ring plus nothing else. Half-integers can appear if the count is odd; that usually means a radical or a counting error.
C: Carbon count in the formula, 6 for C₆H₆.
H: Hydrogen count, 6 for benzene, 14 for a saturated C₆ chain.
N: Nitrogen count. Each N adds like extra hydrogen in the unsaturation formula. 0 if none.
Halogens X: Halogen count (F, Cl, Br, I together). Treat like hydrogen. 0 if none.
DBE: Double-bond equivalents (rings + π bonds).
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