Aim of study: The target of this study was measuring the changes in IFD firmness and thickness values after constant-fatigue loading on the polyurethane (PUR) foams, with six different densities and two different categories, produced in Trabzon/Turkey. Material and Method: The foams were firstly exposed to indentation force deflection (IFD) and constant-fatigue tests based on ASTM D3574 standard. Then, the final IFD values of the foams were determined after loading and the changes in IFD values were reported. Main results: Results indicated that increasing the density of foam in normal category decreased the IFD loss rate in foam firmness. However, this was vice versa for the soft foams. The support factors of normal foams raised as density increased after constant-fatigue loading, however; the support factors of soft foams decreased as the density increased. All foams used in this study indicated a thickness loss lower than 10% after constant-fatigue loading and, no visual failure was detected on the appearances of foams. Highlights: It is important to note that when using a soft foam in a sofa frame, it technically shows opposite behavior both in IFD loss and support factor values under constant-fatigue loading compared to normal foam.