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How Long to Boil an Egg | A Perfect Egg Calculator

Calculates the exact boiling time for the perfect egg based on size, starting temperature, and altitude. Science-backed for precise consistency.

Optional

Higher altitudes lower the boiling point, requiring more cooking time.

Soft-boiled: Jammy texture

Total Boiling Time
6:45
Water Boil Temp 100°C
Egg Category Large

The Science of the Perfect Egg

Cooking an egg isn't just art; it's physics. We use the Charles Williams formula, a heat diffusion equation derived at the University of Exeter. It calculates precisely how long it takes heat to travel through the shell and white to reach the yolk center.

The magic lies in the temperature gap. Egg whites coagulate (set) around 62°C, while yolks remain liquid until about 65°C. Our calculator balances your egg's mass, starting temperature, and atmospheric pressure (altitude) to hit that narrow window perfectly.

How to Boil: The Foolproof Method

  1. Boil the water first. Bring a pot of water to a rolling boil. There should be enough water to completely submerge the eggs by at least an inch.
  2. Lower gently. Using a slotted spoon, gently lower your eggs into the boiling water. Do not drop them. Start the timer immediately.
  3. Maintain a simmer. Lower the heat slightly to maintain a gentle boil. Too violent, and they might crack against the pot.
  4. The ice bath. The moment the timer beeps, transfer eggs immediately to a bowl of ice water for 3 minutes. This stops the cooking and shrinks the egg slightly inside the shell.

The Secret to Easy Peeling

  • Use older eggs. Fresh farm eggs are harder to peel. Eggs bought 1–2 weeks ago are ideal.
  • Thermal shock. The hot-to-cold transition in the ice bath is the single most important factor for separating the membrane.
  • Crack before cooling. Gently tap the shell to crack it before placing it in the ice bath to let water seep between the membrane and the white.

Frequently Asked Questions

Why do my eggs always crack?

This is usually "thermal shock" — dropping a cold egg into boiling water. To prevent it, prick the wider end of the egg with a pin to release air, or use room-temperature eggs.

What is the green ring around the yolk?

That's ferrous sulfide. It forms when you overcook the egg, causing iron in the yolk to react with sulfur in the white. Stick to the timer above to avoid it!