Higher the amount of acid or base used to produce a definite change of pH in a buffer solution, higher will be its buffer capacity.Buffer capacity is maximum under the following conditions.

[Salt] = [Acid] for acid buffer solution and [Salt] = [Base] for basic buffer solution.p^H of a buffer lies in the range of ${\mathrm{p}}^{{\mathrm{k}}_{\mathrm{a}}}\pm 1$. Any buffer solution can be used as buffer up to two units depending on ${\mathrm{p}}^{{\mathrm{k}}_{\mathrm{a}}}$ or ${\mathrm{p}}^{{\mathrm{k}}_{\mathrm{b}}}$ values. When p^H = ${\mathrm{p}}^{{\mathrm{k}}_{\mathrm{a}}}$ or ${\mathrm{p}}^{{\mathrm{k}}_{\mathrm{b}}}$ solution is said to be efficient buffer.