Abstract This paper presents the mechanical properties data of stainless steel at elevated temperatures. Accurate prediction of the material properties of stainless steel at elevated temperatures is necessary for determining the load-carrying capacity of structures under fire conditions. However, full utilization of the special feature of stainless steel has not been possible due to lack of technique data on the fire resistance of stainless steel structural material. Therefore, both steady and transient tensile coupon tests were conducted at different temperatures ranging from approximately 20 to 1000 ∘C to obtained the material properties of stainless steel types EN 1.4462 (Duplex) and EN 1.4301 (AISI 304) with plate thickness of 2.0 mm. The elastic modulus, yield strength obtained at different strain levels, ultimate strength, ultimate strain and thermal elongation versus different temperatures are also plotted and compared with the prediction from the Australian, British and European standards. The test results obtained from this study are also compared with the test results predicted by other researchers. A unified equation for yield strength, elastic modulus, ultimate strength and ultimate strain of stainless steel at elevated temperatures is proposed in this paper. It is shown that the proposed equation accurately predicted the yield strength, elastic modulus, ultimate strength and ultimate strain compared with the test results. Furthermore, stress–strain curves at different temperatures are plotted and a stress–strain model is also proposed.