This study investigates the use of interface Peclet number P = w/(D-l/V-tip), to determine the interface width (w) used in phase-field simulations, where D-l is the liquid diffusivity and V-tip is the tip velocity. The maximum simulation interface width (w(max)) under varied growth conditions was analysed via convergence analysis and it was found that there is a limit of P for the maximum interface width at various velocities. Converged results can be obtained only when w < w(max) = 0.075D(l)/V-max where V-max is the maximum growth velocity during transient solidification. The effect of the inclusion of finite solid diffusivity on the P limit in selecting wmax was analysed, and little influence was observed. (C) 2013 Elsevier B. V. All rights reserved.