How to use the ph calculator
Compute pH, pOH and ion concentrations from hydrogen ion concentration. Enter hydrogen ion concentration [h⁺] in the field above; the ph, poh, [oh⁻] are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “acidity of a solution”, “how acidic”, “hydrogen ion to ph”, “calculate ph”, “find ph”.
Formula
Variables
- H — Hydrogen ion concentration [H⁺] (mol/L)
Worked example
With hydrogen ion concentration [h⁺] = 0.001 mol/L, the calculator gives ph ≈ 3; poh ≈ 11; [oh⁻] ≈ 1 × 10⁻¹¹ mol/L.
Tips for accurate results
- Enter the hydrogen ion concentration in mol/L; 1 mM is 0.001 mol/L.
- The pH and pOH sum to 14 at 25 °C, which the calculator assumes.
- Use this calculator for strong acids and bases; weak acids need an equilibrium calculation.
Common mistakes
- Entering millimolar values as molar, which shifts the pH by 3 units.
- Using this calculator for weak acids, where the hydrogen ion concentration is not the acid concentration.
- Expecting a pH below 0 to be impossible; concentrated strong acids can give negative values.
Frequently asked questions
What is the ph calculator used for?
Compute pH, pOH and ion concentrations from hydrogen ion concentration. It helps with questions such as “acidity of a solution”, “how acidic”, “hydrogen ion to ph”.
What is the formula for the ph calculation?
pH = -log10(H). pOH = 14-[pH]. [OH⁻] (mol/L) = 10^(-[pOH]). Here H is hydrogen ion concentration [h⁺] (mol/L).
What inputs do I need for the ph calculator?
You need hydrogen ion concentration [h⁺] in mol/L. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the ph calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the ph result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.