What is a pH calculator?
A pH calculator relates pH to hydrogen-ion activity and, in a simplified educational calculation, to molar concentration. It also reports pOH and hydroxide concentration. Determine a solution amount first with the Molarity Calculator.
How does this pH calculator work?
For a concentration input, the tool converts to mol/L and takes the negative base-10 logarithm. At 25 °C it uses pH + pOH = 14.000 and [H⁺][OH⁻] = 1.0 × 10⁻¹⁴.
What formulas relate pH and concentration?
pH ≈ −log₁₀[H⁺], pOH ≈ −log₁₀[OH⁻], pH + pOH = 14.000, and [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25 °C. The Scientific Calculator can verify the logarithm.
How do you use the pH calculator?
Select the known quantity, enter one value, and choose the concentration unit when relevant. If the sample came from a stock preparation, use the Dilution Calculator to determine its modeled concentration first.
What do pH results mean?
Lower pH corresponds to greater hydrogen-ion activity on the usual scale, while higher pH corresponds to lower hydrogen-ion activity. The displayed concentration values are mathematical counterparts under the stated approximation, not a laboratory measurement.
Why can measured pH differ from concentration-based pH?
IUPAC defines pH through hydrogen-ion activity, not simply concentration. Activity coefficients, temperature, ionic strength, liquid-junction potentials, calibration, and electrode response can matter. The Percentage Calculator is unrelated to these logarithmic effects.
Who should use this acid-base calculator?
It is appropriate for general chemistry education and approximate dilute aqueous calculations at 25 °C. Buffer systems, weak-acid equilibria, polyprotic systems, titrations, and regulated testing need additional equilibrium constants and validated methods.
Frequently asked questions about pH
Sources and methodology
The calculation method and explanatory context can be checked against these authoritative primary references.