Acids, equilibrium & kinetics · HL

pH, pOH & Kw (HL)

Relate pH, pOH and ion concentrations using Kw.

Your values

Number formats & units

Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.

Calculated locally. No account or input upload.

Example

The calculator is loading. The worked example is also shown below.

Copy & export

K_{\mathrm w}=[\mathrm H^+][\mathrm{OH}^-]

\mathrm pK_{\mathrm w}=-\log_{10}K_{\mathrm w}

\mathrm{pH}+\mathrm{pOH}=\mathrm pK_{\mathrm w}

What the variables mean

Symbol	Meaning
$K_{\mathrm w}$	Ionic product of water at the stated temperature.

pH = 3

Follow the example steps

Use the stated pKw rather than always assuming 14.

pKw = 13.6, pH = 7: pOH = 14 − 7 = 7

pOH = 13.6 − 7 = 6.6

More checks before you submit

Do not automatically set pH + pOH = 14 unless pKw = 14 for the stated conditions.

Method notes

Using Kw explicitly avoids silently assuming 25 °C when another value is supplied.