Perfect use means how well the method works when it’s being tested in a clinical trial by people who are following the instructions perfectly every time they use the method for a whole year and typical use means how well the method works to prevent pregnancy when real people in real life use it.
For example, condoms have a perfect use effectiveness rate of 98% which means that, on average, if 100 people use this method exactly as instructed for a year, two of them will get pregnant. On the other hand, condoms have a typical use effectiveness rate of 87%, which means that, on average, out of 100 people using this method as it’s normally used (aka not perfectly!) for a year, 13 of them will get pregnant.
Since life isn’t a clinical trial, we recommend paying closer attention to typical use numbers. But you can get closer to the perfect use number by learning to use your method correctly and consistently.
Some methods, like the IUD and implant, have a typical use rate that is super close to their perfect use rate—that’s because there’s very little room for error since there’s nothing to do or remember for years once they are placed. (Though of course you can have them removed sooner if you like.) Other methods, like condoms or the pull out method, have a bigger difference between their typical use rate and perfect use rates, because there’s lots more room for error when using these methods.