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pOH Calculator

Enter [OH-] or a pOH value to get pOH, hydroxide concentration, the matching pH and whether the solution is acidic, neutral or basic at 25 C.

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Formula

  • pOH = -log10[OH-] and [OH-] = 10^-pOH
  • pH = 14 - pOH at 25 C
  • pH below 7 is acidic, exactly 7 is neutral, above 7 is basic

Worked example

[OH-] = 0.001 mol/L: pOH = 3, pH = 14 - 3 = 11, so the solution is basic.

pOH 4.5: [OH-] = 10^-4.5 = 3.16 × 10^-5 mol/L and pH = 9.5.

Frequently asked questions

What is pOH?

pOH = -log10[OH-], with [OH-] in mol/L. It is the hydroxide counterpart of pH. For [OH-] = 1.0 × 10^-3 mol/L, pOH = 3.

How do I get [OH-] from pOH?

[OH-] = 10^-pOH. A pOH of 4.5 gives [OH-] = 10^-4.5 = 3.16 × 10^-5 mol/L.

How are pOH and pH related?

At 25 C, pH + pOH = 14. A pOH of 3 means pH 11, which is basic. A pOH of 12 means pH 2, which is acidic.

When is a solution neutral?

When [H+] = [OH-] = 1.0 × 10^-7 mol/L, so pH and pOH are both 7 at 25 C. Pure water is neutral; the neutral point shifts at other temperatures.

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