pOH Calculator

What Is a pOH Calculator?

pOH is the mirror image of pH — it measures hydroxide ion [OH-] concentration instead of hydrogen ion concentration. Since pH and pOH always add up to 14 in water at room temperature, knowing one instantly tells you the other.

How to Use This pOH Calculator

1. Enter either the [OH-] concentration in mol/L, or the pOH value directly — leave the other field blank.
2. Click Calculate to get the corresponding pOH or [OH-], plus the matching pH.

Formula

• pOH = −log₁₀[OH-]
• [OH-] = 10^(−pOH)
• pH + pOH = 14

Worked Example

A solution has [OH-] = 1×10⁻³ mol/L. pOH = −log₁₀(1×10⁻³) = 3, so pH = 14 − 3 = 11 — a basic solution.