The capacity of a sacrificial metal may be calculated from first principle as follows:
* 1 kg Al  = 1000/27 moles Al
* 1 kg Al  = 3 x 1000/27 moles of electrons
* 1 kg Al  = 3 x 1000/27 x 96494 coulombs of charge (by Faraday principles)
* = 10.72 x 10 Amp.seconds of charge per Kg Al   (1 Coulomb = 1 Amp.Second)
* = 10.72 x 10/3600 = 2978 Amp.Hours per Kg
By similar calculations Zinc and Magnesium have a capacity of 825 and 2206 Amp.Hours per Kg respectively.