How the pH calculator works
Enter a hydrogen ion concentration to get pH, or enter a pH to get the concentration. The tool also reports pOH and the hydroxide ion concentration, and tells you whether the solution is acidic, neutral, or basic. pH is defined as the negative base ten logarithm of the hydrogen ion concentration.
The pH scale
The pH scale runs from 0 to 14 in most everyday chemistry. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic, also called alkaline. Because the scale is logarithmic, each whole step represents a tenfold change in hydrogen ion concentration, so pH 4 is ten times more acidic than pH 5.
pH, pOH, and water
In water at room temperature, pH plus pOH always equals 14. So if you know one you know the other, and from either you can find both the hydrogen and hydroxide ion concentrations. The tool computes all four values together so you can move between them without manual logarithms.
Where pH matters
pH governs chemistry in the lab, the body, soil and gardening, pools and aquariums, brewing, and food science. Small pH changes can have large effects because of the logarithmic scale, which is why buffering and careful measurement matter. This tool is for education and general calculation.
Frequently asked questions
How is pH calculated? It is the negative base ten log of the hydrogen ion concentration in moles per liter.
What is neutral pH? A pH of 7 at room temperature, where acid and base are balanced.
What is pOH? The negative log of hydroxide concentration; pH plus pOH equals 14 in water.