The trick to making a perfect boiled egg is all in the timing. Follow these three steps and you can’t fail.
Step 1 Half-fill a small saucepan with cold water. Add a good pinch of 
Step 2 Eggs should be at room temperature (this reduces the risk of cracking). Using a large spoon, lower eggs, one at a time, into boiling water. Stir gently for 30 seconds (this helps to centre the yolks).
Step 3 Reduce heat to medium. For soft-boiled eggs, cook for 4 minutes. For semi-firm yolk and firm white, cook for 5 minutes. For hard-boiled eggs, cook for 8 minutes. Remove with a slotted spoon.