pH Calculator
Calculate pH from H+ concentration, or find [H+] and [OH-] from pH.
pH
pOH
[H⁺] mol/L
[OH⁻] mol/L
How It Works
Enter either the pH value or the hydrogen ion concentration [H+] in mol/L. The calculator uses logarithmic relationships to find pH, pOH, [H+], and [OH-].
Formula
pH = -log₁₀[H⁺] | [H⁺] = 10^(-pH) | pOH = 14 - pH
Examples
pH 7 = neutral | [H+] = 0.01 M → pH 2 (strong acid) | pH 11 → [OH-] = 0.001 M
Frequently Asked Questions
What is pH?
pH is a logarithmic scale measuring hydrogen ion concentration in a solution. pH 7 is neutral; below 7 is acidic; above 7 is basic. It ranges from 0 (most acidic) to 14 (most basic).
How do you calculate pH from concentration?
pH = -log10[H+]. For [H+] = 0.001 M (10^-3): pH = -log(0.001) = 3.
What is pOH?
pOH = -log[OH-]. At 25°C, pH + pOH = 14. A solution with pH 4 has pOH 10.