Calculate cell EMF from half-cell potentials, with the Nernst equation and Gibbs free energy.
Result
How to use this tool
Enter reduction potentials for cathode and anode.
Enter n from the balanced cell reaction.
Read standard EMF and spontaneity.
Enter Q and temperature in Advanced options for non-standard conditions.
Formula & worked example
Copper cathode (+0.34 V) against zinc anode (-0.76 V) gives a standard cell EMF of 1.1 V.
Limitations — read this before you rely on it
Uses tabulated standard potentials at 298 K; junction potentials and activity effects are not modelled.
Frequently asked questions
Yes, using reduction potentials for both half-cells: E°cell = E°cathode – E°anode.
The reaction as written is non-spontaneous and needs an external power supply, as in electrolysis.
E = E° – (RT/nF) ln Q, adjusting the potential for non-standard concentrations.
ΔG° = -nFE°, so a positive EMF gives a negative, spontaneous free-energy change.
E° assumes 1 M concentrations, 1 atm and 298 K; use the Nernst term otherwise.