Buffer Capacity (β)
Buffer capacity is a measure of the ability of a buffer solution to resist changes in pH upon the addition of an acid or base. It is defined as the amount of strong acid or base that must be added to 1 liter of the buffer solution to change its pH by one unit.
β = 2.303 · C · (Kₐ · [H⁺]) / (Kₐ + [H⁺])²