The alkane general formula is the empirical relationship that gives the number of hydrogen atoms in an acyclic (open-chain) alkane containing n carbon atoms. It matters because it lets the molecular formula of any straight- or branched-chain alkane be written from its carbon count alone, and it provides a reference against which unsaturation is measured: each ring or multiple bond reduces the hydrogen count by two relative to this saturated maximum.

烷烃通式是给出含 n 个碳原子的开链烷烃中氢原子数目的经验关系式。它之所以重要,是因为仅凭碳数即可写出任何直链或支链烷烃的分子式,并为衡量不饱和度提供基准:相对于这一饱和上限,每多一个环或一个多重键,氢原子数就减少两个。