A nondimensionalised system commonly used in high energy physics sets ε 0 = c = ħ = 1, where the expressions for the fine-structure constant becomes α α = e 2 4 π π . As such, the fine-structure constant is just a quantity determining (or determined by) the elementary charge : e = √ 4 πα ≈ 0.302 822 12 in terms of such a natural unit of charge.