Cell Potential Calculator (E°cell, ΔG° and K)
By Santaji GadepatilinUpdated November 6, 2026
The standard cell potential of a galvanic cell is the reduction potential of the cathode minus that of the anode; a positive value means the reaction is spontaneous. This cell potential calculator gives E°cell, the standard Gibbs energy change ΔG° = −nFE° and the equilibrium constant K, with a table of standard reduction potentials.
How to use the cell potential calculator
Look up the standard reduction potentials of both half-reactions in the table below. The cathode is where reduction happens (higher E°); the anode is oxidised (lower E°). Enter both values as reduction potentials, the number of electrons in the balanced overall reaction and the temperature.
Cell potential formulas
E°cell = E°cathode − E°anode · ΔG° = −nFE°cell · ln K = nFE°cell / RT
F = 96,485.33 C/mol and R = 8.314 J/(mol·K).
Worked example: Daniell cell
Cu²⁺/Cu cathode (+0.34 V) and Zn²⁺/Zn anode (−0.76 V), n = 2, 25 °C:
- E°cell = 0.34 − (−0.76) = 1.10 V
- ΔG° = −2 × 96,485 × 1.10 = -212.3 kJ/mol
- log₁₀ K = 37.19, so K ≈ 1.54 × 1037
Standard reduction potentials at 25 °C
| Half-reaction | E° |
|---|---|
| F₂ + 2e⁻ → 2F⁻ | +2.87 V |
| Au³⁺ + 3e⁻ → Au | +1.50 V |
| Cl₂ + 2e⁻ → 2Cl⁻ | +1.36 V |
| O₂ + 4H⁺ + 4e⁻ → 2H₂O | +1.23 V |
| Br₂ + 2e⁻ → 2Br⁻ | +1.07 V |
| Ag⁺ + e⁻ → Ag | +0.80 V |
| Fe³⁺ + e⁻ → Fe²⁺ | +0.77 V |
| I₂ + 2e⁻ → 2I⁻ | +0.54 V |
| Cu²⁺ + 2e⁻ → Cu | +0.34 V |
| 2H⁺ + 2e⁻ → H₂ | +0.00 V |
| Pb²⁺ + 2e⁻ → Pb | -0.13 V |
| Sn²⁺ + 2e⁻ → Sn | -0.14 V |
| Ni²⁺ + 2e⁻ → Ni | -0.25 V |
| Fe²⁺ + 2e⁻ → Fe | -0.44 V |
| Zn²⁺ + 2e⁻ → Zn | -0.76 V |
| Al³⁺ + 3e⁻ → Al | -1.66 V |
| Mg²⁺ + 2e⁻ → Mg | -2.37 V |
| Na⁺ + e⁻ → Na | -2.71 V |
| Li⁺ + e⁻ → Li | -3.04 V |
Example cells
| Cell | E°cell | n | ΔG° |
|---|---|---|---|
| Daniell cell (Cu / Zn) | 1.10 V | 2 | -212.3 kJ/mol |
| Silver / copper | 0.46 V | 2 | -88.8 kJ/mol |
| Zinc / hydrogen | 0.76 V | 2 | -146.7 kJ/mol |
| Chlorine / hydrogen | 1.36 V | 2 | -262.4 kJ/mol |
| Silver / zinc | 1.56 V | 2 | -301.0 kJ/mol |
Frequently asked questions
How do you calculate standard cell potential?
E°cell = E°cathode − E°anode, using the standard reduction potentials of both half-reactions as listed in tables. Do not multiply E° by the coefficients when balancing electrons.
How is cell potential related to Gibbs free energy?
ΔG° = −nFE°cell, with F = 96,485 C/mol. A positive E° gives a negative ΔG°, so the reaction is spontaneous.
How do I find the equilibrium constant from E°?
ln K = nFE°/(RT). At 25 °C this is log₁₀ K = nE°/0.05916 V. The Daniell cell (1.10 V, n = 2) has K ≈ 10³⁷.
What about non-standard concentrations?
Use the Nernst equation, E = E° − (RT/nF) ln Q, to correct the cell potential for actual concentrations and temperature.