Chemistry Tools

pH Calculator

Use pH = -log10[H+] or pOH = -log10[OH-] and see the corresponding pH, pOH, H+, and OH- values at 25 °C.

Calculate from

Value

—Uses pH + pOH = 14 at 25 °C and Kw = 1.0×10⁻¹⁴. This is a direct concentration relationship, not an equilibrium solver.

—pH

—pOH

—[H+] mol/L

—[OH−] mol/L

pH / pOH / ion-concentration reverse solver

Solve any one of pH, pOH, [H⁺] or [OH⁻] from another. The default pKw = 14 model is the common 25 °C classroom approximation and can be changed explicitly.

Known quantityValuepKw

—pH

—pOH

—[H+] mol/L

—[OH-] mol/L

Ready.

Interpreting pH and pOH

At 25 °C the calculator uses pH + pOH = 14 and the base-10 logarithm definitions for hydrogen and hydroxide concentration. Very dilute real solutions can require activity corrections and water autoionization treatment, so the simple concentration model is best used for the assumptions stated on the page.