Condoms are cheap, easy to get and pretty good at their jobs. So, they're a practical choice for people who want to have sex without making babies or passing around sexually transmitted infections – as long as they do it right. Male latex condoms, used consistently and correctly, are up to 94 percent effective at preventing the transmission of HIV and other STIs [source: WHO] And as long as they're used consistently and correctly, they're also up to 98 percent effective at preventing pregnancy [source: CDC]. Not too shabby for a simple piece of latex.
Notice that I've already said "consistently and correctly" twice. Fail at either (or both) of those, and condoms are less effective. Case in point: "Up to 98 percent effective" for preventing pregnancy drops to more like 82 percent with imperfect use. And 94 percent drops to 80 percent for STI prevention [source: WHO].
"Consistent" is easy – it means using a condom every time, any time a penis is going into another person's body. (And it's not just for penises: Shared toys need condoms, too.) As for "correct": Condoms seem so straightforward they ought to be foolproof. Like I said, they're just a simple piece of latex. Yet people have found a plethora of ways to do it wrong.
Some of these 10 wrongs could apply to female condoms, dental dams or nonlatex condoms, but I'm sticking with male latex condoms for the sake of simplicity. And I'm going to assume that we're talking about actual condoms here – not jury-rigged substitutes thrown together from things around the house. There are zero right ways to use those.
Let's get started.