What is the chance of pregnancy after taking plan b the morning after?

0.2-3%.: Pregnancy rates of 0.2 to 3% with use of oral emergency contraception and 0.0 to 0.2% with use of copper intrauterine contraception have been reported.

That depends on when: it is taken. 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.