A single, 1-pound lobster should be cooked in boiling water for nine to 15 minutes until it turns bright red. A 2-pound lobster needs to be cooked for a minimum of 15 minutes, while a 3- to 5-pound lobster requires between 25 and 40 minutes.
The cooking time begins after the lobster has been placed in the pot and the water has begun to boil once again. Heavier lobsters turn bright red before they are actually thoroughly cooked, so it is best to cook by time rather than by the appearance of the red on the lobster's shell. If the lobster meat is translucent, clear or runny then the lobster is not finished cooking. The meat should be opaque and completely white.
Lobsters can also be steam-cooked, and although it takes longer to cook thoroughly with this method it is much more difficult to overcook them by steaming. It generally takes between 10 and 20 minutes to properly steam a 1-pound lobster, while a 2- to 5-pound one can require anywhere from 20 to 45 minutes. The cook should remove the lobster from the pot once it has finished cooking and place it on a baking dish or plate with a raised edge to catch the water that drains from the meat as it cools.