pH Mixing Calculator

When two aqueous solutions of different pH are mixed, the resulting pH depends on the hydrogen ion concentrations (for acids) or hydroxide ion concentrations (for bases), weighted by volume.

The pH Scale

pH measures the concentration of hydrogen ions (H⁺) in a solution:

pH = -log₁₀[H⁺]

• pH 0–6: Acidic (more H⁺ ions)
• pH 7: Neutral (pure water at 25°C)
• pH 8–14: Basic/alkaline (more OH⁻ ions)

Each pH unit represents a 10× difference in H⁺ concentration. pH 3 is 10× more acidic than pH 4, and 100× more acidic than pH 5.

Mixing Two Acidic Solutions

When both solutions are acidic (pH < 7), the resulting pH is calculated by combining H⁺ concentrations:

[H⁺]_mix = (V₁ × [H⁺]₁ + V₂ × [H⁺]₂) / (V₁ + V₂)

pH_mix = -log₁₀([H⁺]_mix)

Mixing Two Basic Solutions

For two basic solutions, combine OH⁻ concentrations (using pOH = 14 - pH), then convert back:

[OH⁻]_mix = (V₁ × [OH⁻]₁ + V₂ × [OH⁻]₂) / (V₁ + V₂) pOH_mix = -log₁₀([OH⁻]_mix) pH_mix = 14 - pOH_mix

Acid-Base Neutralization

When an acid and a base are mixed, neutralization occurs: H⁺ + OH⁻ → H₂O. The resulting pH depends on which is in excess. This calculation is more complex and requires knowledge of the buffer capacity and exact concentrations.

This calculator uses the simplified ion concentration approach, which is accurate for dilute solutions without strong buffering agents.

pH Reference