Ionic Strength Calculator
🧪 Solutions & Molarity. Use the Ionic strength formula to find ionic strength, ion 1 concentration, ion 1 charge, ion 2 concentration, ion 2 charge: pick the value you want, type the others, and the answer updates as you go.
Two ions. Default: 0.1 M NaCl.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Ionic strength | mol/L |
| Ion 1 concentration | mol/L |
| Ion 1 charge | no unit |
| Ion 2 concentration | mol/L |
| Ion 2 charge | no unit |
Worked example
Find the ionic strength when Ion 1 concentration = 0.1 mol/L, Ion 1 charge = 1, Ion 2 concentration = 0.1 mol/L, Ion 2 charge = -1.
Using I = 1/2Σ ci zi²: Ionic strength = 0.1 mol/L.
Frequently asked questions
What is the formula for Ionic strength?
I = 1/2Σ ci zi². Two ions. Default: 0.1 M NaCl.
What do the letters stand for, and what units are used?
Ionic strength in mol/L, Ion 1 concentration in mol/L, Ion 1 charge, Ion 2 concentration in mol/L, Ion 2 charge.
How do you calculate ionic strength?
Put the values into I = 1/2Σ ci zi². For example, with Ion 1 concentration = 0.1 mol/L, Ion 1 charge = 1, Ion 2 concentration = 0.1 mol/L, Ion 2 charge = -1, ionic strength = 0.1 mol/L.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (ionic strength, ion 1 concentration, ion 1 charge, ion 2 concentration, ion 2 charge) and fill in the others: it rearranges the formula for you.
