Formula
I=½Σcᵢzᵢ².
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Concentration-based ionic strength. Enter all ions; charge neutrality and activity coefficients are not inferred.
Example Calculation
Example inputs
- Ion concentrations (mol/L): 0.1,0.1
- Signed ionic charges: 1,-1
A solution with 0.1 M of a +1 ion and 0.1 M of a −1 ion has I=0.1 M.
Frequently asked questions
How do I use this calculator?
Enter ion concentrations (mol/l), signed ionic charges. The result updates automatically. Use Reset to restore the example values.
What method does it use?
I=½Σcᵢzᵢ².. Concentration-based ionic strength. Enter all ions; charge neutrality and activity coefficients are not inferred.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.