Calculator
Use standard reduction potentials: E°cell = E°cathode − E°anode. Do not multiply a tabulated potential by its balanced-equation coefficient.
Formula and assumptions
E°cell = E°cathode − E°anode
The calculator subtracts the anode reduction potential from the cathode reduction potential. A positive standard cell potential is spontaneous as written under standard conditions.
Assumption: Both supplied values are standard reduction potentials under standard conditions.
Variables and units
Worked example
Cu²⁺/Cu at +0.34 V and Zn²⁺/Zn at −0.76 V gives E°cell = +1.10 V.
Standard reduction potentials (25 °C)
| Half-reaction | E° (V) |
|---|---|
| Ag⁺ + e⁻ → Ag | 0.8 |
| Cu²⁺ + 2e⁻ → Cu | 0.34 |
| 2H⁺ + 2e⁻ → H₂ | 0 |
| Fe²⁺ + 2e⁻ → Fe | -0.44 |
| Zn²⁺ + 2e⁻ → Zn | -0.76 |
| Li⁺ + e⁻ → Li | -3.04 |
In the Daniell cell copper is the cathode and zinc the anode: E°cell = E°cathode − E°anode = 0.34 − (−0.76) = 1.10 V. Use both values as reduction potentials; do not flip the sign of the anode value and then subtract it again. A positive E°cell means the reaction is spontaneous under standard conditions; real cells give less under load and at non-standard concentrations.
Important limits
It does not calculate non-standard potentials, cell current, resistance or battery capacity.
Reference and related tools
OpenStax: Galvanic cells. Return to Chemistry Calculators for the other tools in this group.