pH from Concentration Calculator
Convert hydrogen ion concentration to pH instantly. This calculator applies the definition pH = -log10[H+] so you can analyse acid or base strength in laboratory reports, titrations, or water quality logs.
For dilute aqueous solutions; actual pH may vary with activity coefficients.
Examples
- [H+] = 1 × 10⁻³ mol/L ⇒ pH 3.00 (strongly acidic)
- [H+] = 2 × 10⁻⁷ mol/L ⇒ pH 6.70 (slightly acidic)
- [H+] = 5 × 10⁻¹¹ mol/L ⇒ pH 10.30 (mildly basic)
FAQ
Can concentration be zero?
No. Because log10(0) is undefined, the concentration must be greater than zero for the formula to work.
What does a lower pH mean?
A lower pH corresponds to a higher hydrogen ion concentration, meaning the solution is more acidic.
Does temperature affect pH?
Yes. The autoionisation of water changes with temperature, so neutrality shifts slightly; this calculator assumes 25°C.
How do I input buffer solutions?
Use the equilibrium [H+] from your buffer calculation or titration curve—this tool converts that value to pH.
Additional Information
- Each whole pH step represents a tenfold change in hydrogen ion concentration.
- Pure water at 25°C has [H+] ≈ 1 × 10⁻⁷ mol/L, corresponding to neutral pH 7.
- For very concentrated or non-aqueous solutions, activity coefficients may be required for precise pH values.
- If you only know hydroxide concentration, convert it using pOH = -log10[OH⁻] and pH = 14 - pOH (at 25°C).
Connect pH back to the mole
When reporting titrations or buffer prep work, cite the mole base unit explainer alongside ISO 80000-9 terms so reviewers understand how every molar concentration traces to the Avogadro constant.
Deepen your pH practice
For guidance on hydrogen-ion activities, electrode care, and traceability, explore the pH activity guide together with our explainers on amount-of-substance concentration and molality so every calculation pairs operational inputs with ISO-coherent reporting.