Nernst Equilibrium Potential Calculator
Enter extracellular and intracellular ion concentrations. An equilibrium potential is calculated when both concentrations are defined and greater than zero.
| Ion | Valence (z) | Extracellular (mM) | Intracellular (mM) | Equilibrium Potential (mV) |
|---|
GHK Membrane Potential
Uses Na⁺, K⁺, and Cl⁻ concentrations from the Nernst table, with editable relative permeabilities.
| Ion | Relative permeability |
|---|---|
| K⁺ | |
| Na⁺ | |
| Cl⁻ |
Enter positive Na⁺, K⁺, and Cl⁻ concentrations on both sides.
GHK voltage equation
Vm = (RT / F) ln
PK[K⁺]o + PNa[Na⁺]o + PCl[Cl⁻]iPK[K⁺]i + PNa[Na⁺]i + PCl[Cl⁻]o
P denotes relative permeability; subscripts o and i indicate extracellular and intracellular concentrations. Chloride terms are reversed because Cl⁻ is negatively charged. This form applies to monovalent ions.
Nernst equation
Eion = (RT / zF) ln([ion]outside / [ion]inside)
R = 8.3145 J·mol⁻¹·K⁻¹; F = 96485 C·mol⁻¹. Concentrations should use the same units; this calculator labels them as mM. Default temperature is 22 °C. Results are rounded to one decimal place.