Calculate buffer pH from the ratio of conjugate base to acid.
A buffer works best when the base-to-acid ratio is near one, which puts the pH at the pK_a. Beyond a tenfold ratio either way — one pH unit — buffering capacity falls off sharply. Choosing a buffer means choosing an acid whose pK_a is within one unit of the target pH; no concentration adjustment can compensate for the wrong pK_a.
Henderson Hasselbalch
pH = pK_a + log₁₀([A⁻] ÷ [HA])
pH = pK_a + log₁₀([A⁻] ÷ [HA]) A buffer works best when the base-to-acid ratio is near one, which puts the pH at the pK_a. Beyond a tenfold ratio either way — one pH unit — buffering capacity falls off sharply.
Choosing a buffer means choosing an acid whose pK_a is within one unit of the target pH; no concentration adjustment can compensate for the wrong pK_a.
This calculator takes 4 inputs: pKa of the acid, Conjugate base concentration, Acid concentration, Buffer volume. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.