and ? is the ionization constant. In other words, one free electron at position X₁ will result in M free electrons at position X₂. Substituting the voltage gradients into this equation results in

Where V is the applied voltage, V_BR is the breakdown voltage and n is an empirically derived value between 2 and 6. As can be seen from this formula, the multiplication factor is very highly dependent on the applied voltage, and as the voltage nears the breakdown voltage