To ensure eggs are perfectly cooked, it is recommended to boil them for 6 to 8 minutes for a soft-boiled egg, 10 to 12 minutes for a medium-boiled egg, and 12 to 15 minutes for a hard-boiled egg. The cooking time varies based on the desired level of doneness, with shorter times resulting in a softer yolk and longer times leading to a firmer texture.

The reason for these specific cooking times lies in the heat's impact on the egg's proteins. When eggs are boiled, the heat causes the proteins in the egg white and yolk to coagulate and solidify. The cooking time determines the extent of this coagulation. A shorter cooking time allows the proteins to coagulate less, resulting in a softer yolk and a more liquid egg white. Conversely, a longer cooking time leads to more extensive protein coagulation, resulting in a harder yolk and a more solid egg white. According to the United States Department of Agriculture (USDA), the recommended cooking times are based on the temperature of the water and the size of the eggs. Water should be brought to a rolling boil before adding the eggs, and the eggs should be submerged in the boiling water. The USDA also advises that the eggs should not be overcooked, as this can lead to a tough texture and a greenish ring around the yolk, which is caused by the iron in the egg white reacting with the sulfur in the yolk.