Even so, a recent study found that the average penis size is about 5.56 inches (14.12 centimeters), but there is considerable variability — with the smallest penis in that study measuring 1.6 inches (4 cm) and the largest sizing up at 10.3 inches (26.2 cm). [7 Wild Facts About the Penis]
By contrast, most condoms sold in the United States average 7 inches (17.7 cm) long, are a few inches bigger than the average penis and come in just a few standardized sizes. The biggest standard condoms are 8.32 inches (21 cm) long.
Because condoms are considered medical devices, they must go through rigorous, standardized testing — typically involving a balloon test where they are filled with water or air until they burst. The organizations that conduct the testing only allow narrow size ranges.
However, several studies have reported that up to half of men find condoms to be too long, too short, too loose or too tight. Poorly fitting condoms can lead to discomfort, slippage and breakage during sex, all of which reduce condom effectiveness. Condoms have a failure rate of about 15 percent with typical use.