First off it depends on the type of accident. If you rear ended the guy in front of you by following too close then yes it will go up. If you hit a deer that crossed your path through no fault of your own or someone rear ended you, then no it won't go up. State insurance boards usually allow insurance companies to charge for a accident for 3 years from the day they started charging for it. Not from the time you got into the accident. If you got in the accident in December and your policy runs from October to April. Your rates won't be affected until April of the next year and the surcharge will drop off 3 years from that April.
How much will your rates go up? You can usually expect a rate increase of between 20-40% on average as per the standard ISO clause, but there is no specific formula that all insurance companies use. They could go up even more if you lose some discounts you were getting, such as a claim free discount. Auto insurance companies are required to file rates with each state insurance department where they operate, and included in that is how they're going to determine rates after a claim is made. In some states, insurance companies are legally required to give you a copy of the "surcharge schedule." However, trying to read these schedules can make your head spin.
Iso has a website at http://www.iso.com/. But what determines your insurance premiums after an accident is 1. what your policy says and 2. what the state insurance regulator approved on the surcharge list for that insurance company.