Egg Boiling Timer

The Egg Boiling Timer tells you exactly how long to boil an egg for the yolk you want — from a runny soft-boiled egg to a firm hard-boiled one — and adjusts the time for your egg size, altitude, and whether the eggs start fridge-cold or at room temperature. Instead of a one-size-fits-all table, it runs a real heat-transfer model and gives you a built-in countdown timer to cook by.

How Long to Boil an Egg

These are typical times for a large, fridge-cold egg dropped into water at a rolling boil at sea level. Bigger eggs, colder eggs, and higher altitudes all add time — enter your own conditions above to get an exact number.

Adding several cold eggs at once briefly cools the water, so if you are boiling a big batch, add roughly a minute for the pot to come back to temperature.

The Science: How This Calculator Works

The timer chains together three pieces of physics rather than guessing from a table:

1. Air pressure at your altitude — from the barometric formula.
2. The true boiling point of water at that pressure — from the Antoine equation. Water boils cooler as you climb.
3. The cooking time for the yolk centre to reach its target — from Charles Williams’ heat-transfer model for a boiling egg.

Here M is the egg’s mass, T_water is the boiling temperature at your altitude, T_egg is the starting temperature of the egg, and T_yolk is the target temperature for the yolk centre. The coef(M) term bundles the egg’s size, density, specific heat, and thermal conductivity.

Why Altitude Matters

Water can never get hotter than its boiling point, and that boiling point drops about 1°C for every 285 m (935 ft) you climb. At 1600 m (Denver) water boils near 95°C; at 2500 m it is close to 92°C. Cooler water transfers heat into the egg more slowly, so the same egg needs noticeably longer. Above roughly 4600 m the water is simply not hot enough to fully set a firm yolk — you would need a pressure cooker, which raises the boiling point back up.

Egg Size and Cooking Time

A jumbo egg has almost twice the mass of a peewee egg, and heat has to travel further to reach the centre. Because the cooking time scales with mass to the two-thirds power, going up one grade adds roughly 30–60 seconds. The calculator uses the USDA minimum in-shell weight for each grade:

• Peewee — 35 g
• Small — 43 g
• Medium — 50 g
• Large — 57 g
• Extra Large — 64 g
• Jumbo — 71 g

What Affects Your Egg Timing

How to Use This Calculator

1. Pick your egg size from Peewee to Jumbo so the model uses the right mass.
2. Choose the doneness — soft, jammy, medium, hard, or very firm — to set the target yolk temperature.
3. Set your altitude and starting temperature (fridge-cold or room temperature).
4. Click Calculate Time to get the exact boiling time, then press Start on the built-in countdown timer while your eggs cook.
5. Ice bath: when the timer beeps, plunge the eggs into ice water to stop cooking and make peeling easy.

Frequently Asked Questions

How long should you boil an egg?

For a large, fridge-cold egg dropped into boiling water at sea level, aim for about 4 to 5 minutes for a soft, runny yolk, 5 to 6 minutes for a jammy ramen-style yolk, and 8 to 10 minutes for a firm hard-boiled yolk. Bigger eggs, colder eggs and higher altitudes all add time, which is exactly what this calculator works out for your conditions.

Why does altitude change egg boiling time?

Air pressure drops as you go higher, so water boils at a lower temperature. At 2000 m it boils near 93°C instead of 100°C, so the water is cooler and the egg takes longer to reach the same yolk temperature. Above roughly 4600 m the water is too cool to fully set a firm yolk without a pressure cooker.

What is a jammy egg?

A jammy egg has a yolk that is heated to about 68°C, so it is thick and marmalade-like: set enough to hold its shape but still soft and spoonable in the centre. It is the classic egg for ramen and grain bowls, and usually takes a minute or two longer than a soft-boiled egg.

Why do hard-boiled eggs get a green ring?

A grey-green ring around the yolk forms when eggs are cooked too long or too hot. Iron from the yolk reacts with sulfur from the white to make iron sulfide. Cooking only until the yolk is just set, then cooling the eggs quickly in ice water, prevents the ring.

Should eggs go into cold or boiling water?

This timer models eggs added to water that is already at a rolling boil, which gives the most repeatable results. A cold-water start, where you bring the eggs and water up to the boil together, works too but the timing depends on how fast your stove heats up, so the boiling-water method is easier to time precisely.

How do you make boiled eggs easy to peel?

Use eggs that are a week or two old rather than very fresh, add them to already-boiling water, and plunge them into ice water for a few minutes as soon as the timer ends. The rapid cooling shrinks the egg from the shell and makes the membrane release cleanly.

Additional Resources

• Boiled Egg - Wikipedia
• Boiling Point - Wikipedia