What is the Nernst equation?

E_ion = (RT/zF) × ln([ion]out/[ion]in). At 37°C: E_ion = (26.7/z) × ln([ion]out/[ion]in) mV. For K⁺ (z=1): E_K = 26.7 × ln(5/150) ≈ −90 mV.

What is the Goldman-Hodgkin-Katz equation?

GHK: Vm = (RT/F) × ln[(Pk[K⁺]o + PNa[Na⁺]o + PCl[Cl⁻]i) / (Pk[K⁺]i + PNa[Na⁺]i + PCl[Cl⁻]o)]. Typical resting Vm ≈ −70 mV for neurons.

What is the resting membrane potential of a typical neuron?

Typical resting membrane potential: −65 to −75 mV. Set primarily by K⁺ permeability via leak channels and maintained by Na⁺/K⁺ ATPase (3 Na⁺ out / 2 K⁺ in per cycle).

Membrane Potential Calculator — Nernst & Goldman Equation

Constant	Symbol	Value	Units
Speed of light	c	2.99792458×10⁸	m/s
Planck's constant	h	6.62607015×10⁻³‴	J·s
Boltzmann constant	kʙ	1.380649×10⁻²³	J/K
Avogadro's number	Nₐ	6.02214076×10²³	mol⁻¹
Gravitational constant	G	6.6743×10⁻¹¹	N·m²/kg²
Gas constant	R	8.31446	J/(mol·K)
Elementary charge	e	1.602176634×10⁻¹⁹	C
Electron mass	mₑ	9.1093837015×10⁻³¹	kg
Proton mass	mₚ	1.67262192369×10⁻²⁷	kg
Fine-structure constant	α	7.2973525693×10⁻³	dimensionless

Formula Definitions

The Membrane Potential Calculator — Nernst & Goldman Equation works by applying a well-defined formula to the values you enter. Understanding the formula behind the calculation helps you interpret the result and check that your inputs are correct. Below we break down the key components that drive the Membrane Potential.

The core formula used by this calculator is:

Result = f(physical quantities, constants, conditions)

Each variable in the formula has a specific meaning:

physical quantities — Measured values with units entered into the Membrane Potential.
constants — Physical or chemical constants (e.g. CODATA values, gas constant, Avogadro's number).
conditions — Temperature, pressure, concentration, or environmental state of the system.
Result — Computed physical or chemical quantity with associated units.

Note: Compare results with standard reference values or published experimental data.

How to Use This Calculator

Enter the physical or chemical quantities. Enter the physical or chemical quantities with correct units into the Membrane Potential Calculator — Nernst & Goldman Equation input fields.
Verify conditions. Verify or adjust the conditions such as temperature, pressure, concentration, or environmental parameters.
Apply the scientific formula. Press Calculate to apply the scientific formula or physical law.
Compare with reference values. Review the result and compare it with standard reference values, CODATA constants, or published experimental data.

Glossary and Definitions

Physical quantity: A measurable property of a physical system, expressed as a numeric value with units.
Constant: A fixed, well-defined value (e.g. a CODATA constant) used across scientific calculations.
Significant figures: The digits in a measurement that carry meaning, reflecting the precision of the instrument.
Reference value: A published standard or experimental value used to validate a calculated result.
Nernst equation calculator: A key concept referenced by the Membrane Potential: Calculate equilibrium potential for individual ions (Nernst) and resting membrane potential (Goldman-Hodgkin-Katz) from ion concentrations and permeabilities.
Goldman equation: A key concept referenced by the Membrane Potential: Calculate equilibrium potential for individual ions (Nernst) and resting membrane potential (Goldman-Hodgkin-Katz) from ion concentrations and permeabilities.
Membrane potential calculator: A key concept referenced by the Membrane Potential: Calculate equilibrium potential for individual ions (Nernst) and resting membrane potential (Goldman-Hodgkin-Katz) from ion concentrations and permeabilities.
Resting membrane potential: A key concept referenced by the Membrane Potential: Calculate equilibrium potential for individual ions (Nernst) and resting membrane potential (Goldman-Hodgkin-Katz) from ion concentrations and permeabilities.

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