To make a hard-boiled egg, the American Egg Board suggests placing one or more eggs into a pot of cold water, then bringing the water to a boil. As soon as the water boils, the heat can be turned off and the eggs allowed to sit in the hot water.
When hard-boiling eggs, the same amount of time is needed no matter the number of eggs. Large eggs need to stand in the hot water after the heat is turned off for 12 minutes, while medium-sized eggs need to be in the hot water for just 9 minutes. Extra large eggs should sit in the hot water for 15 minutes.