Analytical and semianalytical expressions for the growth rate of binary droplets in supersaturated vapour mixtures are derived. The analytical approach is appropriate for continuum regime droplets, the semianalytical approach allows for corrections needed in the transition regime and the Kelvin effect. Both models are based on the assumption of constant and uniform droplet composition, which depends only on a mass flux ratio. The predictions given by the models are compared to the results calculated according to a quasisteady numerical model for water-n-propanol droplets. The approximate models provides reasonable estimations for the growth rate, for the droplet temperature and for the droplet composition when the vapour activities are relatively low, i.e. when the sum of the activities does not strongly exceed unity.