Electrode Potential Converter Calculator

Calculator Inputs

Input Potential

Enter the measured electrode potential.

Input Unit

Input Reference

Target Reference

Output Unit

Electrons, n

Needed for ΔG°, K, and Nernst calculations.

Temperature (K)

Reaction Quotient, Q

Use Q = 1 to keep E equal to E°.

Use converted target potential for cell thermodynamics

Formula Used

Reference conversion to SHE:
E_{vs SHE} = E_input + E_offset,input

Conversion from SHE to target reference:
E_target = E_{vs SHE} - E_{offset,target}

Standard Gibbs energy change:
ΔG° = -nFE

Equilibrium relation:
ln K = nFE / RT

Nernst equation:
E = E° - (RT / nF) ln Q

Constants used: F = 96485.33212 C/mol and R = 8.314462618 J/mol·K.

Reference offsets are treated as 25°C laboratory values. Real offsets vary with filling solution, concentration, and temperature.

How to Use This Calculator

Enter the measured electrode potential.
Choose whether the input is in volts or millivolts.
Select the reference electrode used for the original reading.
Select the target reference scale for conversion.
Pick the output unit you want to display.
Enter n, temperature, and Q if you want thermodynamic outputs.
Tick the thermodynamic option only when the chosen potential represents E°cell for the reaction.
Press Convert Potential to view the result above the form, the comparison table, and the Plotly graph.

Example Data Table

Input Potential	Input Reference	Target Reference	Converted Result
0.250 V	Ag/AgCl (Saturated KCl)	SHE	0.447 V
-0.120 V	SCE (Saturated Calomel Electrode)	Ag/AgCl (3M KCl)	-0.089 V
480 mV	Ag/AgCl (3M KCl)	SCE (Saturated Calomel Electrode)	449 mV
0.315 V	Ag/AgCl (1M KCl)	Ag/AgCl (Saturated KCl)	0.353 V

FAQs

1. What does this calculator convert?

It converts an electrode potential measured against one reference electrode into equivalent values against other common references. It also estimates ΔG°, equilibrium behavior, and Nernst-adjusted potential when you intentionally treat the converted value as a standard cell potential.

2. Why do reference electrodes matter?

An electrode potential is always measured relative to another electrode. Different references have different fixed offsets. The calculator adds the input reference offset, converts the value to the SHE scale, then subtracts the target reference offset.

3. Can I use millivolts instead of volts?

Yes. Choose mV for the input or output unit. The calculator converts units internally, performs all chemistry calculations in volts, and then shows the final displayed values in the unit you selected.

4. When should I use the thermodynamic option?

Use it only when the converted target potential represents the standard cell potential for the reaction of interest. A single half-cell potential versus a reference electrode does not uniquely determine ΔG° or the equilibrium constant for a complete cell reaction.

5. What does a positive converted potential mean?

A positive converted value simply means the target-referenced potential is above that reference on the chosen scale. It does not automatically guarantee spontaneity unless the value is being used as a true full cell potential for the stated reaction.

6. Why does Q change the Nernst-adjusted result?

The Nernst equation corrects E° for nonstandard conditions. When Q differs from 1, the logarithmic term shifts the potential. Higher product-to-reactant ratios usually reduce reduction potential for the reaction as written.

7. Are the reference offsets exact at every condition?

No. The listed offsets are practical laboratory values commonly used around 25°C. Real reference potentials depend on solution composition, chloride concentration, ionic strength, and temperature. Use your laboratory’s validated offset when high-precision work is required.

8. What do the CSV and PDF buttons export?

The CSV file exports the summary and full reference-conversion table. The PDF option captures the results section exactly as displayed, including the main numbers and tables, which is useful for reports, notes, or lab documentation.