The magical power of one person is dependent on the size of the magical core, which itself is under normal circumstances dependent on the body size of the magical wielder, as well as the speed with which raw magic is transformed into ready magic, on the fitness of the wielder and how fast a wand can use that ready magic. The lumos charm is used to measure ones magical power.
Power level Edit
In this story aurors are a power unit as described by Harry when explaining Lord Voldemort's power level. Based on that is the following power level list made:
|10th||Auror security trainee||0.2|
[ v ]Human magic
|Wand based||Alchemy · Charms · Duelling · Transfiguration · Wand lore|
|Wandless||Enchantments · Herbology · Necromancy · Potions · Rituals|
|Mixed||Divination · Healing · Magical theory · Mind magic|