If your hair is dark brown, you won't get to blonde with one bleaching. You might get to a very brassy orange the first time, and may get to a shade of blonde the second or third time---but you'll still have to tone it, because what you get with straight peroxide isn't a very attractive color on most people.
Honestly, I wouldn't try to go from dark brown to blonde at home. I'd go to a salon, and have a professional do it. If you do it yourself, you may end up doing a lot of damage to your hair, and the resulting color may not be one you're happy with.