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pH Calculator — Acidity, pOH and H+ Concentration

Enter a pH, pOH, [H⁺] or [OH⁻] value and this calculator derives the other three, using pH = −log[H⁺] and pH + pOH = 14 at 25 °C. Useful for chemistry coursework, lab prep and titration checks.

How to use pH Calculator

1. Pick which value you know.
2. Enter it (concentrations accept scientific notation).
3. Read the derived pH, pOH and both concentrations.

Frequently asked questions

What is the formula for pH?

pH = −log₁₀[H⁺], where [H⁺] is hydrogen-ion concentration in mol/L. pOH = −log₁₀[OH⁻], and pH + pOH = 14 at 25 °C.

Can pH be negative or above 14?

Yes. Very concentrated strong acids can give a negative pH, and concentrated strong bases can exceed 14. The 0-14 range is a convention, not a limit.

Does temperature affect pH?

Yes. The pH + pOH = 14 relationship holds at 25 °C; the ion product of water changes with temperature.

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