The standard method for boiling eggs in a kettle typically requires 6 to 8 minutes for hard-boiled eggs and 4 to 5 minutes for soft-boiled eggs. The duration depends on the desired level of doneness and the size of the eggs. Hard-boiled eggs are fully cooked and have a solid white and yolk, while soft-boiled eggs have a runny yolk. It's important to note that the water should be brought to a rolling boil before adding the eggs, and the heat should be reduced to a simmer once the eggs are in the water to prevent overcooking.

The reason for these specific times lies in the cooking process and the temperature of the water. When eggs are placed in boiling water, the heat causes the proteins in the egg white to coagulate and the yolk to set. The longer the eggs are cooked, the more the proteins coagulate, resulting in a harder texture. The size of the eggs also plays a role, as larger eggs will take longer to cook than smaller ones. According to the United States Department of Agriculture (USDA), hard-boiled eggs should be cooked at a rolling boil for 6 to 8 minutes for large eggs, while soft-boiled eggs should be cooked for 4 to 5 minutes at a rolling boil. These guidelines ensure that the eggs are cooked to the desired level of doneness without becoming overcooked or rubbery.