pH Calculator
Convert between hydrogen-ion concentration and pH, with pOH and [OH⁻].
pH
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pOH
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[H⁺] (mol/L)
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[OH⁻] (mol/L)
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Classification
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Results update as you type.
About this calculator
The pH of a solution measures its acidity as pH = −log₁₀[H⁺], where [H⁺] is the hydrogen-ion concentration in mol/L. This calculator converts a concentration to pH or a pH back to concentration, and also returns pOH and the hydroxide concentration using pH + pOH = 14 at 25 °C.
Frequently asked questions
What is the pH formula?
pH is the negative base-10 logarithm of the hydrogen-ion concentration, pH = −log₁₀[H⁺]. A concentration of 1×10⁻⁷ mol/L gives a neutral pH of 7.
How are pH and pOH related?
At 25 °C, pH + pOH = 14. So a solution of pH 3 has pOH 11, and its hydroxide concentration is [OH⁻] = 10⁻¹¹ mol/L.
Results are estimates for general guidance only, not financial, medical or tax advice.