Apart from reducing sexual pleasure for both partners, badly fitting condoms are more likely to split or break, researchers say.
Men are twice as likely to take the condom off midway through sex due to a poor fit, a poll of 436 men in Sexually Transmitted Infections journal has revealed.
45% of 436 men questioned by the University of Kentucky researchers reported that their last sexual encounter involved an ill-fitting condom.
The ill-fitting condom reduced sexual pleasure for 120 of the respondents while 57 said it had reduced it for their partner.
The research also revealed that 34 had removed the condom early, and 18 reported that the condom had broken during sex.
Considering the fact that all these problems were far less frequent among men who reported a well-fitted condom, the US researchers concluded that: "Men and their female sex partners may benefit from public health efforts designed to promote the improved fit of condoms."
Simon Blake, from advisory charity Brook, told the BBC that used correctly, condoms were 98% effective and protected against both unplanned pregnancy and sexually transmitted infections. He said: "Standard latex condoms should fit most people but there are many different types of condoms available in different shapes and sizes and trying different types will be important in finding the 'right one'."
Natika Halil, from sexual health charity FPA, told the BBC that men, and women, should take time to learn the skills needed to put a condom on properly.
"Confidence and the skill of putting on a condom also contributes to how well they are used.
"Men come in all shapes and sizes and so do condoms. When we talk with men on the FPA helpline about condoms tearing, slipping off or being a nuisance to use, one of the main culprits is often something as simple as not using the right size."
