An approximate explicit formula for the enhancement factor in the case of irreversible (m,n)th-order gas-liquid reactions is derived. The formula is applicable in both the slow-and fast-reaction regimes. The accuracy of the formula has been tested by comparing it with the exact numerical solution of the film model. The comparison is made over wide ranges of the Hatta number, ratio of bulk liquid concentration to interfacial concentration of the gaseous reactant, and other parameters of the reaction system. The overall mean percentage deviation of the approximate formula is within 5% for m = 1 and integer orders n in the range [1,3], while the deviation is within 19% for n = 1 and integer orders m in the range [1,3].