Egg's size...
US M
... or weight
oz
Egg's origin
Custom ▾
... or initial temperature
°F
Altitude
ft
Boiling point of water
212
°F
Air pressure
1.0132
bar
Quarter-boiled egg boiling time
5
min
9
sec
Soft egg boiling time
7
min
47
sec
Half-boiled egg boiling time
8
min
44
sec
Hard egg boiling time
10
min
51
sec

Egg Boiling Calculator

By Miłosz Panfil, PhD and Mateusz Mucha

Everyone cooks eggs differently. What sets this egg calculator apart is that it was created by Miłosz Panfil, Omni Calculator's chief scientist, who happens to have a PhD in Quantum Physics from the University of Warsaw.

If you want to boil the perfect egg according to quantum physics, use our calculator and follow these steps:

  • Bring the water to a boiling point.
  • You may add half a teaspoon of table salt to help prevent the eggs from cracking. For the same reason, it's better to use eggs that aren't taken straight out of the fridge.
  • Be generous with the amount of water; inserting the egg lowers the temperature, we want to be sure we're at the boiling point! Once the eggs are in the water, start the timer.
  • When the time is up, take the eggs out of the pot and rinse them with cold water to stop the boiling process.

That's the recipe in a nut(egg?)shell, but what's the science behind it?

The science behind the boiling of an egg

When we place anything in hot water it gets warmer, eggs included. The water begins by warming the shells of the eggs and then their interior, which consists of the white which surrounds the yolk. A soft-boiled egg should have a firm white and a runny yolk. While both the white and yolk coagulate (change from liquids to gels) in hot water, the white coagulates at a slightly lower temperatures than the yolk. So, for a soft-boiled egg, we should heat the egg to a temperature where the white have already thickened but the yolk has not. The calculator assumes that we get a perfect soft-boiled egg when it reaches a temperature of 65C (149F). So how much time does it take to heat an egg to this temperature?

As soon as the eggs are in water, the shell's temperature quickly reaches that of the boiling water. The heat then starts to spread throughout the egg. This process is controlled by a heat diffusion equation which depends on two parameters: the heat conductivity and heat capacity. The heat conductivity specifies how quickly the heat spreads, while the heat capacity tells us how much heat we need to warm up the substance by one degree. From the heat diffusion equation, we can estimate the time t when the temperature between the white and yolk reaches our 65C. That's when we stop heating the eggs. Because the white is still at a noticeably higher temperature (the shell has a temperature of 100C/212F) even if we take the eggs out of the water, there will still be some heat transferred from the white to the yolk, meaning the yolk might coagulate. That's why we should cool down our eggs immediately after taking the eggs out of the water - so we stop the boiling process.

A precise calculation of the time required to cook a perfect soft-boiled egg is difficult. The whites and yolk are complicated substances involving various types of proteins and fat molecules. Also, every egg is different, and the ratio of whites to yolk varies. Charles Williams of the University of Exeter came up with a formula involving all the main factors. The time for the region between the white and yolk to get to a temperature T, is

t = m * K * log(ywr * (T_egg - T_water)/(T - T_water))

where

  • m is the mass of the egg,
  • K is the factor describing thermal properties of an egg,
  • T_egg is the initial temperature of the egg,
  • T_water is the temperature of the water,
  • T is the temperature in the region between whites and yolk,
  • ywr is a ratio of white to yolk.

For a soft-boiled egg, the temperature T should be 65 degrees Celsius (149 F), so that's the value set in our calculator. For a hard-boiled egg, the temperature inside the egg should be higher, so the yolk coagulates. However, it cannot be too high because then the sulfur in the white reacts with the iron in the yolk and creates the greenish ferrous sulfide covering the yolk. To avoid it we should keep the temperature T bellow 77 Celsius (170.6 F).

The altitude? Is it a joke?

Why there is an altitude section in our calculator? The higher above the sea level you are, the more air pressure decreases, and therefore the boiling point of water decreases. That makes the cooking process more time-consuming. If you are high enough, like Mount Everest high, you won't get hard-boiled eggs. Water boils at 8848m (29029 ft) above sea level at a disappointingly low temperature of 68 degrees Celsius (154.5 F). For a more real-world example, a Bolivian city of El Alto, a home to over 1 million people, is 4150 meters above the sea level. Water boils at 85.9 Celsius (186.6 F), which translates to approximately 2.5 minutes longer soft-boiling time. That's crazy!

Life hacks: how to peel an egg like a pro!

Of course you can just crack the egg and then peel it, piece by piece, but why would you do it that way when you could just use one of these three time-saving hacks?

  1. Once your egg has cooked and cooled down just enough for you to touch it, open it up at both ends. Then, just blow it out of the shell! Just watch how this guy does it:
  1. If you don't have that much lung power, put the egg in a container filled with water, close it and shake really well. The peel will come off on its own.

  2. Want to try the third option? Crack the egg and roll it on the counter for a few seconds. Then, peel it while holding it in cold water. Works like a charm!

Miłosz Panfil, PhD and Mateusz Mucha

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