Buffer Capacity Calculator
Enter the amount of strong acid or base added, the buffer's volume, and the pH before and after. The calculator returns the empirical buffer capacity, the amount of strong acid or base per liter needed to shift the pH by one unit.
Last updated: September 26, 2026
Frequently asked questions
What is buffer capacity?
Buffer capacity (β) measures how much strong acid or base a buffer can absorb before its pH changes significantly. A higher β means the buffer resists pH change more strongly.
Is this a theoretical or measured value?
This calculator computes an empirical (measured) capacity from the pH change you observed after adding a known amount of acid or base. It is not a prediction from concentration alone.
Why can't ΔpH be zero?
Buffer capacity is defined as the amount added divided by the resulting pH change. If the pH didn't change, the capacity would be undefined (infinite), so the calculator requires a nonzero change.
Does one buffer capacity value apply everywhere?
No. Capacity depends on the buffer's concentration, the ratio of acid to conjugate base, and how close the starting pH is to the buffer's pKa. Capacity is highest near pH = pKa.
How is this related to the Buffer pH Calculator?
The Buffer pH Calculator estimates a buffer's pH from its composition using the Henderson-Hasselbalch equation. This calculator instead measures how resistant an existing buffer is to a pH change.
Does this tell me how to prepare a buffer?
No. It only computes capacity from measurements you provide and gives no preparation or handling instructions.