How to use it
Choose the quantity you know and enter its value. Concentrations are in mol/L. Read pH, pOH, and both concentrations.
Method and worked example
pH = −log₁₀[H⁺]; pOH = −log₁₀[OH⁻]. This page uses pH + pOH = 14 as a 25°C dilute-water classroom approximation.
Example
[H⁺] = 1×10⁻³ mol/L gives pH 3, pOH 11, and [OH⁻] = 1×10⁻¹¹ mol/L.
Assumptions and limitations
Concentration must be positive. pH need not be confined to 0–14 for concentrated solutions. This tool does not infer pH from bulk acid concentration, account for activity, weak-acid equilibria, buffers, temperature-dependent water ionization, or laboratory safety.
Privacy and accessibility
Calculations run in this browser session. This page does not send, store, or add your entered values to a URL. Controls work with a keyboard and results and errors are announced as text.