The flame jet width and flame jet velocity of the burnt gases of a premixed Bunsen-type flame are important parameters for quantifying the heat-transfer rates of these flames. In this paper a simple expression is derived to estimate the flame jet width and flame jet velocity of burnt gases of a free flame after expansion over the flame front for the special case of plug flow in and above the burner. The results of particle image velocimetry experiments on three different flame types having different oxygen concentrations are presented. The model is validated with these measurements and shows good agreement. Deviations occur, however, when the curved flame front area of the flame tip is not negligible compared to the total flame area. (c) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.