🧫pH & pOH Calculator

Convert between pH, pOH, [H⁺], and [OH⁻] using pH + pOH = 14 and [H⁺][OH⁻] = Kw.

pOH

[H⁺] (mol/L)

[OH⁻] (mol/L)

Kw (leave default for 25°C)

Free pH & pOH Calculator

Our free pH calculator chemistry tool converts instantly between pH, pOH, [H⁺], and [OH⁻]. Enter any one of the four values and it calculates the other three using the standard 25°C relationships pH + pOH = 14 and [H⁺][OH⁻] = Kw, with an option to adjust Kw for non-standard temperatures.

Switch to strong acid/base mode to enter a molar concentration directly and get its pH immediately, assuming full dissociation. Results display in proper scientific notation, and a visual acid-base scale shows exactly where your solution falls between strongly acidic and strongly basic.

Ideal for chemistry homework, lab prep, or a quick sanity check — runs entirely in your browser. No sign-up, no downloads, no limits.