1 If you like your eggs medium-boiled, remove them from the water in 5-7 minutes. The yolks should be semi-soft in the very center and the whites should be very firm.  If you like your eggs hard-boiled, leave the eggs in the hot water for up to 10-15 minutes.
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I put my eggs in the water before I put the pan on the stove. If you wait until the water boils to put the eggs in, the shells will immediately crack open and the egg will run out. I boil my eggs for 10-12 minutes, depending on whether they're large eggs or extra large eggs. Once they are done, run some cold water into the pan and drain out the boiling water.
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I always bring the water up to a boil and then put the eggs in. I let them cook until one of the cracks or for about 7 mins. an egg takes about 15-20 minutes to boil. Boil the water, then put the eggs in for 10 mins.
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1 When the water just starts to simmer, turn off heat, cover pan with a lid, and let stand for 17 minutes. Don't peek.  Pour out the hot water and pour cold water over eggs. Drain and refill with cold water; let stand until eggs are cool, about 20 minutes. Peel eggs under running water.
http://allrecipes.com/recipe/235595/how-to-make-perfect-hard-boiled-eggs/
Hard-boiled eggs are great for deviled eggs, egg salad, or on their own as a protein-rich and filling snack. However, if you always end up with cracked eggs and green yolks when you try to make hard-boiled eggs, you're not getting the most of your eggs. Luckily, there are ways to guarantee delicious eggs every time.
http://www.wikihow.com/Hard-Boil-an-Egg
1 Stirring the eggs a couple of times while the water is coming to a boil helps center the yolk and ensure even cooking.  When you boil the eggs make sure the water is at boiling point. Cook the egg for 12 minutes for a large, 15 minutes for an extra large.
http://www.wikihow.com/Hard-Boil-an-Egg
I let the eggs sit in the cool water for a few minutes, then remove them and put them in a bowl in the frig so that they get cold. I always put into cold water and bring to the boil and then reduce heat to a simmer and cook for 7-10 minutes. If you want to shell them drain and run under cold water for several minutes to chill them, or just leave in a pot of cold water.
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Compared to a simmer, here’s what a rolling boil looks like. 3) Let the eggs stand in the hot water for 14-17 minutes. How long you let the eggs stay in the water depends on how big the eggs are and how hard you want them cooked. To cook small eggs to medium, let them stand for 14 minutes. To cook extra-large eggs to medium, let them stand for 17 minutes. (We’re talking about chicken eggs here.
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Once all the eggs are added, cover the bowl with a lid or a plate. Let it sit — the eggs will cook in the heat of the near-boiling water. Your cooking time will vary depending on how hard you want your eggs. In general, you should expect your eggs to take slightly more time than they would on the stove.
http://www.wikihow.com/Hard-Boil-an-Egg
1 Place eggs into a saucepan and pour in cold water to cover; place over high heat. When the water just starts to simmer, turn off heat, cover pan with a lid, and let stand for 17 minutes. Don't peek.  Pour out the hot water and pour cold water over eggs.
http://allrecipes.com/recipe/235595/how-to-make-perfect-hard-boiled-eggs/
how long should i cook an egg to hard boil
You cook an egg for 10 to 15 minutes to hard boil. You should cook an egg for 10 to 15 minutes to hard boil. It takes 10 to 15 minutes to cook an egg to hard boil.