How effective is plan b if i took it after 40 hours?

Effective: Plan B is more effective the sooner it is taken. Within the first 24 hours it is 95% effective. This falls to 85-87% at 72 hours.

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.