Heat flux sensor calibration is often expensive, but it is also a fundamental step to obtain valid results. According to the needs, several calibration procedures could be considered. If experimental interpretations focus on heat flux values comparison rather than true values, a relative calibration with high accuracy can be performed. This paper focuses on a new relative calibration-type method of heat flux sensors (HFSs). In general, the HFSs were originally (even recently) factory and in-house-calibrated, but this method was used to calibrate them to an exact common reading to help in performing accurate experiments and eliminating errors that could result from differences between the HFSs. The developed methodology was adapted from a secondary calibration-type (i.e., absolute) generalization. This method aimed to present a simple, low cost, and accurate way to calibrate heat flux sensors. The proposed calibration method was relative, which means that it did not use any calibration reference. However, an absolute calibration adaptation of this method can easily be performed. In the method presented in this paper, calibration was made via sensor sensitivity correction. The experiment consisted of imposing an identical and homogeneous heat flux across four heat flux sensors during a sufficiently long time to be able to statistically subtract any unwanted influences, such as convective and radiative variation. More precisely, temperatures and heat flux levels of 30-35 °C and 60-70 W.m -2 , respectively, were used. Then, new sensor sensitivity values were found by basic statistical data manipulations. Although the focus of this methodology was for contenting thermopile-based HFSs that used differential temperature measurements, the set-up can be adapted for other types of HFSs. In this paper, the set-up, its conception, and guidelines for using this method are presented.