New expressions for the mass burning rate are derived from a recently introduced flamelet model using integral analysis. The results are compared with well-known expressions, based on large-activation-energy asymptotics. There is no restriction on Lewis numbers and the expressions reduce to the same results as found earlier with asymptotic techniques for Lewis numbers close to 1. From our analysis it appears that the burned edge of a stretched flamelet is most appropriate to determine the mass burning rate. The consequences for experimental and numerical studies are investigated.