pOH Calculator — pOH = −log[OH⁻]

pOH is the mirror of pH for bases: lower pOH means more hydroxide and a more basic solution. At 25 °C, pH + pOH = 14, so either scale fully describes the solution.

pOH Calculator — pOH = −log[OH⁻]

$pOH = -\log_{10}[OH^-]$

Solve for

Hydroxide-ion concentration ([OH⁻])

Unit

Result unit

How to interpret the result

Worked check: [OH⁻] = 1.0×10⁻⁴ M → pOH = 4.00, which corresponds to pH 10.00 at 25 °C. pOH below 7 means basic; above 7 means acidic.

Assumptions

Aqueous solution near 25 °C
Activity approximated by concentration