pH to pOH Online Calculator

In any aqueous solution, there is H+ and OH- ions. When H+ ion concentration is changed, OH- concentration also is changed. Multiplication of H+ ions andOH- ions is a constant value at a specified temperature. In this calculator, you can calculate OH-concentration of aqueous solution, when H+ concentration of that solution is known.



Please follow below two basic steps.

  1. Select the temperature (Neutralized pH at standard temperature 250C is 7)
  2. Enter H+ ion concentration and calculate it.





pOH value

In the answer, sometimes you may see term such as e-[number]. In those cases, this means × 10-number.

As an example, if answer is given as, 1e-13, it means 1 × 10-13



How to calculate OH- concentration from H+ concentration? Take the temperature as 250C

Because [H+] × [OH-] = constant, OH- concentration can be calculated using H+ concentration and constant. This constant value depends on temperature and for 250, it is 1.0 * 10-14 mol2 dm-6 .

Let's take H+ concentration of an aqueous solution as 0.1 mol dm-3 at 250C.

  • [H+] × [OH-] = 1.0 * 10-14
  • 0.1 × [OH-] = 1.0 * 10-14
  • [OH-] = 1.0 * 10-13 mol dm-3






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