Nernst Equation Calculator
Nernst equation calculator: cell potential under non-standard conditions from E°, temperature, electrons transferred and Q.
E = E° − R · Tz · F · ln Q
How to use this calculator
- Choose the quantity you want under “Solve for”.
- Type the known values and pick their units: any combination works.
- The result updates as you type. Open “Show the steps” to see the substitution.
The Nernst equation gives the potential of an electrochemical cell away from standard conditions: E = E° − (RT/zF)·ln Q, where Q is the reaction quotient and z the electrons transferred.
At 25 °C, RT/F = 25.69 mV, so the familiar form is E = E° − (0.05916 V/z)·log₁₀Q. When the cell reaches equilibrium, E = 0 and Q = K.
Formula
E = E° − R · Tz · F · ln Q
| Symbol | Quantity | Units |
|---|---|---|
| E° | Standard cell potential | V, mV, µV, kV |
| T | Temperature | K, °C, °F, °R |
| z | Electrons transferred | — |
| Q | Reaction quotient | — |
| E | Cell potential | V, mV, µV, kV |
Constants used: R = 8.314462618 J·mol⁻¹·K⁻¹ · F = 96,485.33212 C·mol⁻¹
Worked example
Given: E° = 1.1 V · T = 25 °C · z = 2 · Q = 0.01
E = E° − R·Tz·F ln Q
Result: E = 1.15916 V
Frequently asked questions
How do I get the equilibrium constant from E°?
Set E = 0 and solve for Q: K = e^(zFE°/RT).
What is Q for a Daniell cell?
For Zn + Cu²⁺ → Zn²⁺ + Cu, Q = [Zn²⁺]/[Cu²⁺]. Pure solids are left out.