How effective is plan b is taken 8 hours after condom breaks?

Very: When taken within 24 hours of unprotected intercourse, Plan B is up to 95% effective at preventing pregnancy. If you take Plan B and don't get your period in 3 weeks, you should take a pregnancy test just to be on the safe side. Best of luck!

Plan B: Plan B One-Step is up to 89 % effective when taken within 72 hours (3 days) after unprotected sex. It can reduce chance of pregnancy by up to 95% if used within 24 hours. It continues to reduce the risk of pregnancy up to 120 hours (5 days) after unprotected sex, but is less effective as time passes.