pOH Calculator
Compute pOH, pH, [H⁺], and [OH⁻] from a single input. Default Kw=1.0×10⁻¹⁴ (25 °C). Use a custom Kw to model other temperatures/conditions.
pOH Calculator
This tool links pH, pOH, hydrogen ion concentration [H⁺], hydroxide ion concentration [OH⁻], and the ionic product of water Kw. At 25 °C, Kw=1.0×10⁻¹⁴ so pH+pOH=14, but Kw changes with temperature and composition; when Kw changes, the sum pH+pOH equals pKw=−log₁₀Kw, and the neutral point is pH=pKw/2. Pick a single known quantity—pH, pOH, [H⁺], or [OH⁻]—and the calculator derives the rest using base-10 logarithms. Concentrations spanning many orders of magnitude are rendered in scientific notation for readability, and you can switch between three and six significant figures. Minor differences after rounding can make [H⁺][OH⁻] deviate slightly from Kw; the consistency line indicates how close the product is to the chosen Kw.
How to use
- Choose a mode (Given pH, pOH, [H⁺], or [OH⁻]).
- Select Standard (25 °C) or enter a custom Kw.
- Enter your value and choose precision (3 or 6 significant figures).
- Click Calculate to see pH, pOH, [H⁺], [OH⁻], and pKw.
- Download a TXT summary or a one-page PDF.
Formula notes
pH = −log₁₀[H⁺]; pOH = −log₁₀[OH⁻]; pH + pOH = pKw (where pKw=−log₁₀Kw).
[H⁺] = 10^(−pH); [OH⁻] = 10^(−pOH); [H⁺][OH⁻] = Kw.
Disclaimer. Educational use only. Not a substitute for professional judgment.
