Enter your Buffer Type, Equilibrium Constant, Acid Concentration [HA], Base Concentration [A⁻], and Temperature to calculate your Buffer pH — plus secondary outputs like Concentration Ratio, Log(ratio), and Buffer Capacity to give you a fuller picture of your buffer system's behavior.
Buffer pH
--
Concentration Ratio
--
Log(ratio)
--
Buffer Capacity
--
Select your buffer type (acid or base), enter the pKa or pKb value, input the concentrations of both components, and the calculator will compute the pH using the Henderson-Hasselbalch equation.
A buffer is a solution that resists changes in pH when small amounts of acid or base are added. It consists of a weak acid and its conjugate base, or a weak base and its conjugate acid.
Use the Henderson-Hasselbalch equation: pH = pKa + log([A⁻]/[HA]) for acid buffers, or calculate pOH = pKb + log([BH⁺]/[B]) then pH = 14 - pOH for base buffers.
An acid buffer consists of a weak acid (HA) and its conjugate base (A⁻). A base buffer consists of a weak base (B) and its conjugate acid (BH⁺).
A buffer works most effectively when the pH is within ±1 pH unit of its pKa value. The buffer capacity is highest when pH = pKa.
Common buffer pKa values include: acetate (4.76), phosphate (7.21), Tris (8.06), and bicarbonate (6.35). These values are typically measured at 25°C.
Temperature changes can affect pKa values and thus buffer pH. Most pKa values decrease slightly as temperature increases, so buffer pH may change with temperature.
Buffer capacity measures how much acid or base a buffer can neutralize before significant pH changes occur. Higher concentrations and pH closer to pKa result in greater buffer capacity.