Standard Cell Potential Calculator
E°cell, ΔG° and K from two reduction potentials.
Work out Standard Cell Potential. E°cell, ΔG° and K from two reduction potentials. Shows every step's contribution, not just the total.
Straight from the reduction potential table. Cu²⁺/Cu is +0.34, Ag⁺/Ag +0.80.
Also the REDUCTION potential — do not flip its sign. Zn²⁺/Zn is −0.76.
Standard cell potential
+1.1 V
Spontaneous as written — a galvanic cell
E°cell = E°cathode − E°anode, with both values taken straight from the reduction potential table. The anode's sign is not flipped first — the subtraction already does that. Flipping it and then adding does the same operation twice and gives an answer wrong by exactly twice the anode potential, which is the single commonest error in electrochemistry. Cell potential is intensive: it does not depend on how much material there is, and it is not multiplied when you scale the equation. Only ΔG° scales, through n. The K value shows why a modest voltage means a reaction that goes essentially to completion — 1.10 V over two electrons gives K around 10³⁷.
How the Standard Cell Potential Calculator works
Enter both electrode potentials straight from a standard reduction table — including the anode's, unflipped — and this gives the cell potential, the free energy change and the equilibrium constant. Flipping the anode's sign before subtracting does the same operation twice.
Also known as: e cell calculator · galvanic cell calculator · emf of a cell calculator · cathode minus anode calculator
Frequently asked questions
How do I calculate standard cell potential?
E°cell = E°cathode − E°anode, with both taken as reduction potentials from the table. The Daniell cell is 0.34 − (−0.76) = 1.10 V.
Do I flip the sign of the anode potential?
No. The subtraction already reverses it. Flipping it first and then subtracting applies the reversal twice and gives an answer wrong by exactly twice the anode potential — the commonest error in the topic.
Does cell potential change if I double the equation?
No. Potential is intensive, like temperature or density — it does not depend on how much material there is. Only ΔG° scales, because n changes.
What does a positive E°cell mean?
The reaction is spontaneous as written, so the cell is galvanic and produces current. Negative means it needs driving, making it electrolytic. A modest 1.10 V corresponds to an equilibrium constant around 10³⁷.
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