Buffer Capacity Calculator
Estimate the buffer capacity of a weak-acid/conjugate-base buffer from the acid and base concentrations.
How it works
β ≈ 2.303 · ([HA] · [A⁻]) / ([HA] + [A⁻])
Buffer capacity measures how much strong acid or base a buffer can absorb before its pH shifts by one unit. This simple form peaks when the acid and conjugate base concentrations are equal (a 1:1 ratio, at pH = pKa) and grows with the total amount of buffer present. It is expressed in moles of H⁺ or OH⁻ per litre per pH unit.
Worked example
For [HA] = 0.10 mol/L and [A⁻] = 0.10 mol/L: β = 2.303 × (0.10 × 0.10) / (0.10 + 0.10) = 2.303 × 0.05 = 0.115 mol/(L·pH).
Sources: Buffer solution — Wikipedia
Frequently asked questions
When is buffer capacity greatest?
When the acid and its conjugate base are present in equal concentrations, which is where pH equals the pKa. Moving away from a 1:1 ratio lowers the capacity.
How do I increase a buffer's capacity?
Use more concentrated buffer components while keeping the ratio near 1:1. Capacity scales roughly with the total concentration of the buffer pair.
Is this the exact buffer capacity?
It is the widely used simple approximation that ignores the contribution of water's own H⁺ and OH⁻. That term only matters at extreme pH or very dilute buffers.
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