Egg Boiling Time Calculator

Get the right boiling time for soft, medium, or hard-boiled eggs, adjusted for egg size, starting temperature, and altitude.

Quick Facts

Method
Heat-conduction scaling: time scales with egg mass to the 2/3 power
Reference times (large 57g egg, sea level, from fridge): 6 min soft, 8 min medium, 12 min hard.

Your Results

Calculated
Boiling time
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Minutes at a rolling boil
Boiling time (seconds)
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For precise timers

Ready

Enter your egg size and doneness, then calculate.

How egg boiling time is actually calculated

An egg cooks from the outside in: heat has to conduct through the shell, the white, and finally into the yolk. Because of this, boiling time does not scale linearly with egg size — it scales with the egg's mass raised to the power of two-thirds (t ∝ m^(2/3)), which is the standard relationship for heat conduction into a roughly spherical object of uniform density. Double the mass of an egg and the boiling time increases by about 59%, not 100%, because the increase in surface area (through which heat enters) is smaller than the increase in volume (which needs to be heated).

The reference times this calculator uses

For a large egg (57 g) starting cold from the refrigerator and cooked at a rolling boil at sea level, widely used culinary reference times are approximately 6 minutes for soft-boiled (runny yolk, just-set white), 8 minutes for a medium/jammy yolk, and 12 minutes for a fully hard-boiled yolk. This calculator scales those reference times for your actual egg weight using t = t_ref × (m / 57)^(2/3), where t_ref is the 6/8/12-minute baseline and m is your egg's weight in grams.

Adjusting for starting temperature

An egg taken straight from the refrigerator (roughly 4°C / 40°F) needs more time to reach the same internal doneness than one that has been left at room temperature (roughly 20°C / 68°F), because more of the cooking time is spent simply raising the egg's internal temperature before the "cooking" transition even begins. This calculator adds about 30 seconds when you select a fridge-cold egg, reflecting typical kitchen-tested adjustments; using a room-temperature egg lets you shave that time back off.

Adjusting for altitude

Water boils at a lower temperature as atmospheric pressure drops with elevation — roughly 1°C (about 1.8°F) cooler for every 300 meters (roughly 1,000 feet) of elevation gain. Since egg proteins set at specific temperatures, a lower boiling point means the water is doing less work per minute, so eggs need extra time at altitude to reach the same doneness. This calculator adds a proportional time correction based on the elevation you enter, using the same ~1°C per 300 m relationship.

Why this differs from a simple lookup table

Most recipe cards give a single number ("boil for 10 minutes") because they assume one specific egg size, one starting temperature, and sea-level cooking. In reality, a jumbo egg (71 g) needs noticeably longer than a small egg (43 g) for the same doneness, and a mountain kitchen needs longer than a beach kitchen. Scaling by mass and correcting for temperature and pressure gets you much closer to a consistent, repeatable result across all these conditions.

Frequently Asked Questions

Why does a bigger egg need more than proportionally more time?
Heat has to conduct in from the shell, so cooking time is governed by the egg's surface-to-volume ratio, not its raw mass. That relationship works out to time scaling with mass to the 2/3 power — so a 71 g jumbo egg needs about 15% more time than a 57 g large egg, not the 25% you'd get from a simple weight ratio.
Should I start the eggs in cold water or add them to already-boiling water?
This calculator assumes eggs go into already-boiling (or already at a rolling simmer) water, which is the method most cooking references use for consistent, repeatable timing. If you start eggs in cold water and bring the pot up to a boil together, total time will run longer and less predictable, since the ramp-up period varies by pot, stove, and water volume.
Why did my egg come out differently than the calculated time?
The most common causes are an egg temperature that wasn't accounted for (fridge vs. counter), water that wasn't at a full rolling boil when the timer started, a very fresh egg (fresh eggs can cook slightly differently than week-old eggs due to air-cell size), or stopping the cook without an ice-water shock, which lets residual heat keep cooking the yolk for another minute or two after you drain the pot.

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