pH Calculator
Calculate pH, pOH, and ion concentrations for acids, bases, and buffers
How to use pH Calculator
- 1Enter the hydrogen ion concentration, or the acid and its concentration.
- 2Choose whether to compute pH, pOH, or convert between them.
- 3Read the pH and what it implies about acidity or basicity.
The pH scale
pH = -log10[H+]; pOH = 14 - pH (at 25 C)pH is the negative base-10 logarithm of hydrogen ion concentration, so each unit is a tenfold change in acidity.
A pH below 7 is acidic, 7 neutral, above 7 basic; the scale is temperature dependent and the 0 to 14 range is typical for water-based solutions.
Frequently asked questions
Why is pH logarithmic?
Because ion concentrations span many orders of magnitude, a log scale keeps them on a handy 0 to 14 range.
Is 7 always neutral?
Neutral is where pH equals pOH; at 25 C that is 7, but the neutral point shifts with temperature.
Can pH be negative?
Yes, very concentrated strong acids can have pH below 0, though that is unusual in everyday contexts.
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