Unpinning of spiral waves from circular and rectangular obstacles of various sizes under electrical forcing was investigated in both the Belousov-Zhabotinsky reaction and numerical simulations with the Oregonator model. The used rectangles had a similar area size but different circumferences by adjusting width and height, while the area of the circles increased with the circumference. The results showed that for both cases the necessary strength of forcing for unpinning increased with the circumference. This implies that for such unpinning the circumference has a higher impact than the area, at least for circular and rectangular obstacles. (C) 2016 Elsevier B.V. All rights reserved.