The preforming of textile reinforcements during composite manufacturing is subject to significant variability, which affects the predictability of critical defects such as wrinkles in the component. Therefore, wrinkling variability needs to be quantified so that it can be accounted for during production and in process simulations. This study characterises the variability in the wrinkling behaviour of a biaxial non-crimp fabric during hemispherical preforming under various conditions. A variability characterisation method is developed that decouples and quantifies the variability in wrinkle amplitude and wrinkle location. The results show that the fabric architecture and the specific forming layup have a significant influence on both the wrinkle amplitude and location variability, with the location variability being more sensitive to changes in the forming process than the amplitude variability. The method can be applied to characterise the variability for various surface defects or variables and thus used as a benchmarking tool for preforming processes.