The secret to knowing if a hard-boiled egg is done lies in the timing. You see, if you overcook an egg, it can become rubbery and taste pretty bland. But, if you undercook it, the yolk can be too runny and just plain gross.
So, how do you get it just right? Well, the general rule of thumb is to boil the egg for about 10-12 minutes for large eggs. But, this can vary depending on the size of the egg and your personal preference for yolk doneness. Some people like their yolks super runny, while others prefer them fully set.
Another way to check if a hard-boiled egg is done is to use the spin test. Yes, you read that right - spin the egg! If it spins smoothly, it's likely done. But, if it wobbles all over the place, it's probably not cooked enough. It's a pretty cool trick that'll make you feel like a pro in the kitchen.
How Do I Know If A Boiled Egg Is Done at Thomas Schnell blog