How effective is plan b one step if taken within an hour? and how effective are condoms alone?

Very: Plan b taken within 1 hours is going to have an effectiveness rate of around 80-85%. That is if a woman were ovulating at that time, she would have 80-85% chance of preventing pregnancy. Condoms alone are around 75% effective, meaning if taken over course of 1 year between a couple, chance of pregnancy is 25% if they use every time and use perfectly. Hope that helps!