pOH to Hydroxide Concentration Calculator
Convert a pOH value into the hydroxide ion concentration [OH⁻] in mol/L, with matching pH and [H⁺].
How it works
[OH⁻] = 10^(−pOH) · pH = 14 − pOH · [H⁺] = 10^(−pH)
pOH mirrors pH for the hydroxide ion: it is the negative base-10 logarithm of [OH⁻], so raising ten to the negative pOH recovers the concentration. The ion product of water links the two scales through pH + pOH = 14 at 25 °C, so any pOH also fixes the pH and [H⁺].
Worked example
For pOH 4: [OH⁻] = 10⁻⁴ = 0.0001 mol/L. Then pH = 14 − 4 = 10, so the solution is basic, and [H⁺] = 10⁻¹⁰ mol/L.
Sources: Self-ionization of water — Wikipedia
Frequently asked questions
When is pOH more convenient than pH?
For basic solutions you often know [OH⁻] directly — for example from a strong base like NaOH. Working in pOH avoids an extra conversion before applying pH + pOH = 14.
What pOH means a basic solution?
At 25 °C a pOH below 7 (pH above 7) is basic, a pOH above 7 is acidic, and pOH = 7 is neutral.
Is this exactly the reverse of a pOH calculator?
Yes. A pOH calculator turns [OH⁻] into pOH; this tool turns pOH back into [OH⁻] and rounds out the pH and [H⁺].
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