The $\mathrm{pH}$ of a solution is defined as

The pH of a solution is defined as $\mathrm{pH}=-\log \left(\left[{\mathrm{H}}^{+}\right]/{\mathrm{moldm}}^{-3}\right)$

The amount of $\mathrm{H}+\left(\mathrm{aq}\right)$ ions in a solution is indicated by the pH scale. However, using the $\log \left(10\right)$ function makes the calculations simpler. The concentration of $\mathrm{H}+$ ions can be expressed in mol $\mathrm{dm}(-3)$. The concentration of hydrogen ions in an aqueous solution is expressed as the negative logarithm of pH to base 10.