It doesn’t matter how long it is, it’s the girth that counts. This statement isn’t from the rantings of a woman’s magazine column; it’s referring to condoms.

To help men size themselves up correctly, a health clinic in Stockholm, Sweden, is giving its visitors measuring tapes and advice on how to do it properly, the Guardian reports. And this isn’t so they can post their scores on social media; it’s to help them find the right size condom.

If a condom is too big, or too small, for your penis, it won’t fit properly. This increases the chance it might slip off or break during sex, thus compromising its effectiveness. But even if you’re sporting something that could poke someone’s eye out, if the circumference is small, you may need to get a slim-fitting condom, such as Durex’s “conform.” Similarly, if your soldier doesn’t stand quite as tall as most others, but your diameter is above average, you might need to step up to king size.

Anyone who passes the clinic can pop in and ask for the tape, which is designed to measure circumference, not length. Of course, it should be used while the penis is erect, not flaccid. Once men give staff at the center their measurement, they can be advised on the best size for their penis, providing maximum comfort and effectiveness.

So if wearing a condom has been a bit like one of the step-sisters trying to squeeze into Cinderella’s shoe, but you don’t happen to live in Sweden, you can whip out a measuring tape and DIY at home. Your pharmacist should be able to advise you on what’s best for your girth.