What Is a Buffer Solution?

A buffer solution calculator uses the Henderson-Hasselbalch equation to compute the pH of a buffer made from a weak acid and its conjugate base. Buffers resist pH change — when you add acid, the conjugate base neutralizes it; when you add base, the weak acid neutralizes it. That stability is why buffers regulate blood pH, maintain enzyme activity, and calibrate laboratory assays.

The Henderson-Hasselbalch Equation

pH = pKa + log₁₀([conjugate base] ÷ [weak acid]). The pKa is a property of the acid; the ratio is set by how you prepare the solution. When the two concentrations are equal the ratio is 1, the log term is 0, and pH equals pKa — the point of maximum buffering.

Choosing a Buffer

Pick an acid whose pKa sits within one unit of your target pH. Acetic acid (pKa 4.76) buffers around pH 4–5.6; phosphoric acid's first proton (pKa 2.15) and second (pKa 7.20) cover acidic and neutral ranges; carbonic acid (pKa 6.35) buffers near blood pH. The closer the target pH is to the pKa, the stronger the buffer.