Hydrogen Ion Concentration Calculator

About this calculator

pH is defined as the negative base-ten logarithm of the hydrogen ion concentration, so reversing the definition gives [H+] = 10 raised to the power of negative pH, expressed in moles per liter. Because water’s autoionization constant at 25 °C fixes pH plus pOH at 14, this calculator also derives pOH as fourteen minus pH and then the hydroxide ion concentration [OH-] as 10 raised to the power of negative pOH, using the same logarithmic relationship.

Chemistry students, lab technicians, and environmental analysts use these conversions constantly: a water-quality lab reporting a stream’s pH needs the underlying ion concentrations to assess corrosivity or aquatic toxicity thresholds, and anyone preparing a buffer solution or interpreting a titration curve needs to move fluently between pH and molar ion concentrations.

Enter a pH value and this calculator returns the hydrogen ion concentration, the pOH, and the hydroxide ion concentration in one step, saving the manual logarithm and exponent calculations.