Use Nernst Membrane Potential when you need to compute the Nernst equilibrium potential at 37 degrees Celsius in millivolts: EMV = (61.5 / z) x log10(outsideConcentration / insideConcentration), signed positive for outward cation gradient driving force. Enter Ion valence, Outside concentration, and Inside concentration using the definitions and units below so the result can be reproduced.

Ion valence

Ion charge magnitude, an integer from 1 to 3.

Outside concentration

Extracellular concentration in mmol/L; must be greater than zero.

Inside concentration

Intracellular concentration in mmol/L; must be greater than zero.

The published tool contract uses this rule: Compute the Nernst equilibrium potential at 37 degrees Celsius in millivolts: EMV = (61.5 / z) x log10(outsideConcentration / insideConcentration), signed positive for outward cation gradient driving force.

Membrane potential

Signed equilibrium potential in millivolts.

A ratio or percentage can conceal the scale of its numerator and denominator and becomes sensitive to measurement error when the denominator is small. Ion valence must remain between 1 and 3.

Retain the original Ion valence, Outside concentration, and Inside concentration values and their units alongside the result. Goldman Equation is useful when you instead need to compute the Goldman-Hodgkin-Katz steady-state membrane potential at 37 degrees Celsius with the z=+1 cation form for potassium and sodium and inverted terms for chloride: VM = 61.5 x log10((pK x KOut + pNa x NaOut + pCl x ClIn) / (pK x KIn + pNa x NaIn + pCl x ClOut)) mV. Donnan Potential provides another view by helping you compute the equilibrium potential at 25 °C from the inside-to-outside concentration ratio. The base-10 Nernst factor is 59.16 mV per tenfold concentration gradient and is divided by ion valence.

• Goldman Equation

  Compute the Goldman-Hodgkin-Katz steady-state membrane potential at 37 degrees Celsius with the z=+1 cation form for potassium and sodium and inverted terms for chloride: VM = 61.5 x log10((pK x KOut + pNa x NaOut + pCl x ClIn) / (pK x KIn + pNa x NaIn + pCl x ClOut)) mV.

• Donnan Potential

  Compute the equilibrium potential at 25 °C from the inside-to-outside concentration ratio. The base-10 Nernst factor is 59.16 mV per tenfold concentration gradient and is divided by ion valence.

• MSI Percent

  Compute membrane stability as one minus the ratio of initial to boiled conductivity times 100, requiring a positive boiled conductivity and an initial conductivity that does not exceed it.