For something so simple, condoms actually come with a lot of room for error. Most people don’t even know they’re making any.

Body + Soul rounded up the most common mistakes according to sexual health experts, and the list covers everything from how you store them to when you put them on. The fixes are easier than the errors, at least. Here’s what to know.

Putting It On Too Late

This is the big one. Sexual Health Victoria medical director Dr. Sara Whitburn says the most common mistake is waiting too long. “Sperm and sexually transmitted infections can be present in pre-ejaculate, so it is important that a condom is placed on the penis before there is any penetrative contact,” she explained to Body + Soul.

Queensland-based sexologist Isiah McKimmie agrees, adding that the penis needs to be fully erect before putting one on. If you lose an erection during sex, replace the condom. If it doesn’t fit properly, it doesn’t protect properly.

Getting the Size Wrong

A condom that’s too loose can slip off. One that’s too tight can break or become uncomfortable enough to discourage use altogether. A loose fit can also leave enough space for semen to escape, which defeats the entire point.

Dr. Whitburn recommends measuring both length and girth with a flexible tape measure. Sizing is primarily based on girth: snug-fit condoms range from 49-52mm, standard from 52-56mm, and larger sizes from 56-60mm.

Melbourne-based vulvovaginal specialist naturopath Jessica Lloyd says, “Penis owners, you need to experiment on your own and find the right fit for your equipment, so when the time comes, you are not caught out.”

Storing Them Wrong

The wallet condom is a cultural institution and a terrible idea. Heat, friction, humidity, and direct light all degrade condom materials over time.

“Having a condom in your wallet or pocket for a long time can cause the materials to become brittle, less stretchy, and prone to breaking,” Dr. Whitburn says. Lloyd adds that wallets and back pockets are fine for short periods, but cool and dry storage is the actual goal. If a condom has been through the washing machine, throw it out.

Using Expired or Damaged Condoms

Check the date. Lloyd is unambiguous: “The expiry date is on there for a reason. Condoms are not like canned food and will not last into the apocalypse.”

Before use, do a quick visual check for tears, holes, or anything that feels brittle, sticky, or dried out. Dr. Whitburn also warns against cutting packets or tearing them with sharp objects or nails, both of which can damage the condom before it’s even on.

Using the Wrong Lubricant

Oil-based products break down latex. That includes coconut oil, body lotion, and anything else that seems convenient in the moment.

Water-based and silicone-based lubricants are safe with latex condoms. Non-latex condoms have broader compatibility. McKimmie says if there’s any doubt, water-based is always the safest call.

Not Using Enough Lubricant

Pre-lubricated condoms exist, but that factory coating usually isn’t enough, especially during longer sessions.

Lloyd explains, “A dry condom is a recipe for damage to the condom and the vagina or vulva.” Extra lubrication reduces friction, lowers the risk of breakage, and makes the whole experience more comfortable. Adding more is almost never the wrong move.