The influence of the Kelvin effect on droplet growth is theoretically considered. A dimensionless number to characterize the influence of the Kelvin effect on droplet growth rates is defined, The exact calculation of this number requires a numerical solution. Here, an analytical expression to calculate the dimensionless number approximately is derived. The deviation of the analytical solution from the exact numerical solution is investigated, A defined limit when the Kelvin effect can be neglected is given by the dimensionless number. So the radius or the supersaturation for which the influence of the Kelvin effect is negligible can be easily determined by using the analytical expression. This is shown for example for droplet growth in the continuum regime. Furthermore, it is shown that droplet growth in the continuum regime can be highly influenced by the Kelvin effect for low supersaturations not far from the critical supersaturation.