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pH Calculator
Estimate pH, pOH, hydrogen-ion and hydroxide-ion concentrations for a simple strong or monoprotic weak acid/base solution.
How do I calculate pH?
For a strong acid model, pH = −log₁₀[H⁺]; for a strong base, pOH = −log₁₀[OH⁻] and pH = 14 − pOH at 25 °C. Weak monoprotic models solve the mass balance and Ka/Kb equilibrium, including water autoionization. For example, [H⁺] = 1 × 10⁻⁷ mol/L gives pH 7 in this ideal 25 °C model.
Frequently asked questions
How do I calculate pH?
For a strong acid model, pH = −log₁₀[H⁺]; for a strong base, pOH = −log₁₀[OH⁻] and pH = 14 − pOH at 25 °C. Weak monoprotic models solve the mass balance and Ka/Kb equilibrium, including water autoionization. For example, [H⁺] = 1 × 10⁻⁷ mol/L gives pH 7 in this ideal 25 °C model.
Are my concentrations uploaded?
No. The calculation runs in this browser; values are not uploaded or saved by this tool.
What is the difference between pH and pOH?
At 25 °C in this ideal model, pH describes hydrogen-ion concentration and pOH describes hydroxide-ion concentration; their values add to 14.
Can this calculate every acid or base?
No. It supports ideal strong acid/base concentration estimates and one-step monoprotic weak acid/base equilibrium. It does not model polyprotic acids, buffers, salts, activity coefficients or titration curves.
Is this a measured pH value?
No. It is a simplified calculation, not a measurement. Real pH is defined using hydrogen-ion activity, and temperature and solution composition matter. Use an appropriate calibrated method when an actual measurement is needed.