Head-related transfer functions (HRTFs) are essential for personalised binaural audio reproduction and have been defined at the blocked ear canal for reasons originating in acoustic measurements. With the possibility to numerically calculate HRTFs, they can be investigated at the eardrum, given an accurate representation of the geometry of the ear canal. In our study, we evaluated the contribution of the ear canal to the sound localisation in the horizontal and median plane. We used meshes of head and pinnae including ear canals to calculate HRTFs at both the blocked ear canal and the eardrum. The resulting HRTFs showed spectral differences of up to 30 dB in frequency regions above 3 kHz. Simulations obtained with an auditory model for the sagittal-plane sound localisation showed non-negligible differences in the predicted localisation performance. Based on these results, the applicability of numerically calculated HRTFs for binaural audio reproduction and sound localisation experiments is discussed.