According to a recipe from chef Alton Brown, a baked potato should be cook for one hour at 350 degrees Fahrenheit. When properly cooked, the outer skin should be crisp but the inside should feel soft.
Brown also notes that if you are cooking more than four potatoes, the total cook time should be extended 15 minutes. To be sure that a potato is fully cooked, use a food thermometer, and make sure the internal temperature is at least 210 degrees Fahrenheit.
A potato may also be baked in the microwave. This method takes anywhere from six to 12 minutes, depending on the potato size and power of the microwave.