A whole lobster needs to boil in a large pot for 12 to 18 minutes. The water the lobster is boiled in should be salted.
Soft shell lobsters have a shorter cooking time than those with hard shells and cook an average of 3 minutes faster. If the antenna of the lobster pull off easily, they are done cooking.
Lobsters should be placed into boiling water one at a time. Once emerged the water needs to return to a full boil. It is advised that 2 1/2 quarts of water be used for each lobster.
Steaming lobsters is another popular cooking method. This method requires 18 to 20 minutes cooking time.