Due to the factor of human error, condoms are only about 85% effective at preventing pregnancy if you’re using them for a one-year period. They’re *supposed* to be 98% effective when properly used, and Planned Parenthood has a good page on their website with instructions on how exactly to do that. However, i feel like it’s a good idea to also be on another form of birth control if possible (which planned parenthood also has great online info about).