Egg slide rule

The one kitchen utensil you did not yet own...

The physicist Charles Williams of Exeter University has a published formula[1] that solves an old problem: how long should you boil an egg.

The formula looks like this:

The formula assumes that the water is already boiling before the egg is put into the water, and that the process takes place at an air pressure of 1 atmosphere.

The following constants apply.[3]

It is not easy to use this formula in the kitchen. A slide rule would be a great help. However, I have never seen an egg boiling slide rule, not even in the patent literature.

Therefore I offer here my own design of an egg slide rule:[4]

Move the arrow of the Tegg-slide to the weight, choose the Tegg-scale corresponding to your taste, locate the initial temperature of the egg and read the cooking time above this temperature value. For convenience, standard refrigerator temperature * and room temperature [] are highlighted on the Tegg-scale. The EU standard weight classes[5] are indicated below the weight scale.

In the derivation of the formula several approximations are used, like the egg being spherical, and not cooking at a high altitude.

So use the results with a pinch of salt.


A Dutch version of this paper appeared in MIR 50, april 2009.