3 Apr 2009

Egg cooking calculator

As this year's Easter greeting, Deptartment of Chemistry at the University of Oslo has developed an egg cooking calculator with reference to Martin's Khymos and my Maturfag ("Norwegian fooducation").

The issue of cooking the perfectly boiled egg has been discussed several places, amongst others on Khymos, fooducation, and on "Maturfag" which is fooducation's teacher resource pages at the Norwegian Centre for Science Education (Google translation of the resource pages here). Also, Douglas Baldwin's Practical guide to sous vide cooking has an excellent section on controlled-temperature cooking of eggs.

Formula for calculating the boiling time for eggs. For details and
references, see Khymos egg boiling post

Now, Department of Chemistry in Oslo has converted this formula into an interactive animation/calculator for cooking your Easter egg the way most people do it: in boiling water. This has already collected some attention, amongst others in the national newspaper VG (and supposedly on radio at the national broadcasting corporation NRK during Easter holiday). The cooking time depends on several factors, taken that you use boiling water:
  • egg size (circumference around the thick end)
  • initial temperature of the egg
  • altitude (since temperature of boiling water varies according to this)
  • the way you like your egg (soft, hard, medium)

The categories should be rather self-explaining. Click the illustration to go to the calculator
(I love the nifty automatic timer function

Tip: For measuring the circumference of the egg, use a piece of string and measure the length that goes around the "belly" of the egg.

Happy Easter holidays


  1. This is pretty nice from an engineer point of view ;-)
    Does this formula infers the water to already boil when you place the egg.
    Should the egg be cooled right after the cooking time via cold water?

  2. Haha, really nice flash calculator :) Just gotta love it. Happy Ea(s)ter!

  3. Mathieu:

    I recommend Martin's web page over at khymos for details (reference in the blogpost). Quick answers:

    - the water temperature is considered constant, or else the equation would have been far more complicated, taking into account power, heat transfer, amount of water etc.

    - yes, the egg should be cooled at least below the target temperature, since cooking in boiling water will result in a hotter white than yolk, which will lead to continued heat transfer inwards unless the egg is cooled.

    What is not discussed here is the risk of cracking the shell. Dropping the egg into boiling water increases the risk of a cracked shell, but immersing the blunt end of the egg in the water until bubbling ceases will help.

    Of course, this does not apply for steamed eggs using egg cookers

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