How this calculator works
Use both half-cell values as reduction potentials measured against the same reference electrode. Subtract the anode reduction potential from the cathode reduction potential. Do not reverse the anode sign before this subtraction, and do not multiply potentials by balancing coefficients. Standard input potentials produce a standard cell EMF; potentials corrected for actual activities produce the corresponding nonstandard value. This open-circuit thermodynamic estimate excludes ohmic loss and electrode overpotential under load.
Formula
Ecell = Ecathode,reduction - Eanode,reduction.
Worked example
With cathode reduction potential +0.34 V and anode reduction potential -0.76 V, cell EMF is +1.10 V. If cathode is +0.80 V and cell EMF is +1.20 V, the anode reduction potential is -0.40 V.
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Frequently asked questions
Should I change the anode sign?
Enter its tabulated reduction potential directly; the formula performs the subtraction.
Do coefficients multiply voltage?
No. Electrode potential is intensive and does not scale with reaction coefficients.
Is this the loaded terminal voltage?
No. Current-related losses can lower the measured terminal voltage.