pH and pOH Calculator with Steps
Use this free pH and pOH calculator to calculate pH, pOH, hydrogen ion concentration [H⁺], or hydroxide ion concentration [OH⁻]. This tool is useful for acids, bases, equilibrium, and Grade 11–12 chemistry practice.
Calculate pH, pOH, [H⁺], or [OH⁻]
pH and pOH Formulas
pH measures how acidic or basic a solution is. pOH is related to the hydroxide ion concentration. At 25°C, pH and pOH usually add to 14.
pOH = -log[OH⁻]
pH + pOH = 14
A pH below 7 is acidic, a pH of 7 is neutral, and a pH above 7 is basic.
Worked Example
Find the pH of a solution with hydrogen ion concentration [H⁺] = 0.001 mol/L.
The solution has a pH of 3, so it is acidic.
Practice Question
A solution has pH = 4. What is the pOH?