We consider a recent paper by Aghamohammadi (2011 Eur. J. Phys. 32 633) focused on the calculation of the electric potential due to a uniformly charged square. The author of this paper applied a dimensional analysis approach to study the electric potential created by a uniformly charged square sheet on its plane. In this letter, we point out that several exact results presented in the above-mentioned paper can be obtained in a very transparent way by an alternative method we had earlier developed to study the same problem. © 2011 IOP Publishing Ltd.