The On Cloud X3 tends to look good for a run, but one might find it running a size too long. If one wears thinner socks and prefers the shoes to be tighter, it is better to order a size down. However if one wears thicker socks or does not mind the shoes being a bit loose then their regular size should not be a problem as well. The best way to avoid any such discomfort is to try them before purchasing.