Buffer Capacity Calculator
Estimate the buffer capacity of a solution — how well it resists pH change — from the amount of strong acid or base added, the buffer volume, and the resulting pH shift. Enter your values to get the buffer capacity in mol/L per pH unit.
Formula
Buffer Capacity β = (Added strong acid/base concentration) ÷ ΔpH
- Buffer capacity (β) measures how much strong acid or base a buffer can absorb before its pH changes significantly.
- It's calculated as the moles of acid or base added per litre, divided by the resulting change in pH.
- A higher β means a stronger buffer that holds its pH more steadily.
- Capacity is greatest when the buffer's pH equals its pKa (equal acid and conjugate base).
- Enter the acid or base amount in moles, the buffer volume in litres, and the observed pH shift.
0.01 mol acid in 1 L, ΔpH 0.2
Inputs
- Added Acid/Base (mol): 0.01
- Buffer Volume (L): 1
- Observed ΔpH: 0.2
Concentration added = 0.01 ÷ 1 = 0.01 mol/L. Buffer capacity β = 0.01 ÷ 0.2 = 0.05 mol/L per pH unit.
Frequently asked questions
What is buffer capacity?
It's a measure of a buffer's resistance to pH change — how many moles of strong acid or base it can absorb per litre before its pH shifts by one unit.
How is buffer capacity calculated?
Divide the concentration of strong acid or base added (mol/L) by the change in pH it causes. The result is β in mol/L per pH unit.
When is buffer capacity highest?
At the buffer's pKa, where the concentrations of the weak acid and its conjugate base are equal, the buffer resists pH change most effectively.
How can I increase buffer capacity?
Increase the total concentration of the buffer components, or work closer to the buffer's pKa.
What units does the result use?
Buffer capacity is expressed in moles per litre per pH unit (mol/L/pH).