Tin oxide powders were prepared by a homogeneous precipitation method using an aqueous solution of SnCl4 with urea and followed by a calcination process for the crystalline phase. The calcination method affects the crystalline properties of the tin oxide powders in terms of crystallinity and crystalline size. The degree of crystallinity strongly increases as the calcination temperature increases. In comparison with other calcination methods, the rapid thermal annealing (RTA) method yields a high specific surface area and a smaller crystalline size of the tin oxide powder than that achieved by the conventional furnace annealing method. In the RTA process, crystallinity increases as the calcination temperature increases and the ramp‐up speed to reach a designated temperature decreases. Copyright © 2012 John Wiley & Sons, Ltd.