pH Calculator
Calculate pH from [H+] or reverse the relationship to obtain hydrogen-ion concentration from a pH value.
pH6
[H⁺]1.0000e-6 mol/L
pOH (25°C assumption)8
[OH⁻]1.0000e-8 mol/L
How this tool works
pH = −log₁₀[H+]. At 25°C for dilute aqueous solutions, pH + pOH ≈ 14.
Example
A hydrogen-ion concentration of 1×10⁻⁶ mol/L corresponds to pH 6.
Common questions
Is pH + pOH always exactly 14?
No. The 14 relationship depends on the temperature-dependent ion product of water and is a common 25°C approximation.
Does concentration equal activity in every solution?
No. Accurate pH in concentrated or high-ionic-strength solutions requires activities and activity coefficients.