Ionic Strength Calculator

Ionic Strength Calculator

The Ionic Strength Calculator computes the ionic strength of an electrolyte solution from the concentrations and charge numbers of all ions present.

$$I = \frac{1}{2} \sum_i c_i z_i^2$$

where $I$ is ionic strength (mol/L), $c_i$ is the molar concentration of ion $i$, and $z_i$ is its charge number.

Example: a 1 M ZnCl₂ solution gives $c(\text{Zn}^{2+}) = 1$ mol/L and $c(\text{Cl}^-) = 2$ mol/L, so $I = \frac{1}{2}(1 \times 2^2 + 2 \times 1^2) = 3.0$ mol/L.

Ionic strength affects activity coefficients, Debye-Hückel theory, electrochemical measurements, and stability constants. Higher ionic strength generally means ions behave less like ideal particles in solution.

Related tools: Cell EMF Calculator, Electrolysis Calculator, and Concentration Calculator.