As marinera said. Also, try experimenting with the angles of your hips, and other variables, to see what yields the longest measurement. I always recommend optimizing all parameters (standing rather than sitting, thrusting hips forward a bit, angling the penis down to parallel with floor, etc.) to achieve the longest measurement possible, so that you can’t possibly fool yourself into imagining “gains” in the future that may be due to “improved” measurement technique :-) Small differences in these types of things can make a 0.5” or more difference in your length measurement. Anyway, this is just for PE (growth)-tracking purposes. For figuring out how long you are relatively to “average penis size” statistics, I’d suggest a more conservative measurement technique where you don’t try to squeeze out every last tenth of an inch :)