Why do pH and pOH sum to 14?

At 25°C the ion product of water (Kw) is 10⁻¹⁴, and since pH + pOH = pKw, they sum to 14 at that standard temperature.

pH to pOH Calculator

At 25°C, pH and pOH always sum to 14 in water. Convert between the two using this relationship.

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Formula

pOH = 14 − pH (at 25°C)

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