Model resting potential with flexible permeability inputs. Switch temperature units, validate ranges, and see warnings. Download tidy tables and share calculations with colleagues easily.
This sample uses common physiological values. Your results may differ based on tissue and conditions.
| Temp | Pk | Pna | Pcl | K+ in | K+ out | Na+ in | Na+ out | Cl− in | Cl− out | Vm (mV) |
|---|---|---|---|---|---|---|---|---|---|---|
| 37 °C | 1 | 0.04 | 0.45 | 140 | 5 | 15 | 145 | 10 | 110 | −67.34 |
Tip: changing Pna upward typically makes Vm less negative.
The calculator uses the Goldman-Hodgkin-Katz voltage equation:
Vm = (R·T/F) · ln( (Pk·[K]out + Pna·[Na]out + Pcl·[Cl]in) / (Pk·[K]in + Pna·[Na]in + Pcl·[Cl]out) )
The Goldman equation estimates membrane voltage when several ions contribute. It is widely used to model resting potentials, where K+, Na+, and Cl− dominate the electrical balance across a thin membrane.
Concentration gradients provide the driving force, but permeability controls how strongly each ion influences voltage. Increasing Pk makes Vm more negative, while increasing Pna generally depolarizes Vm toward zero.
Chloride is an anion, so its terms appear “swapped” compared with cations. Using [Cl−]in in the numerator and [Cl−]out in the denominator reflects the opposite charge sign in the electrochemical balance.
Vm scales with temperature through the RT/F factor. At 37 °C (310.15 K), RT/F is about 26.7 mV, so small ratio changes can shift Vm noticeably. Cold conditions typically reduce magnitude of predicted voltages.
Many mammalian cells have high intracellular K+ (≈120–150 mM) and low extracellular K+ (≈3–6 mM). Sodium is often opposite: low inside (≈5–20 mM) and high outside (≈135–155 mM). Chloride varies by cell type.
A negative Vm means the inside is negative relative to outside. If you observe a Vm near −60 to −80 mV with the sample ratios, the inputs are consistent with common resting conditions in excitable tissues.
Adjust one parameter at a time to understand sensitivity. Raising extracellular K+ from 5 to 10 mM can markedly depolarize Vm. Similarly, increasing Pna from 0.04 to 0.1 can shift Vm upward by several millivolts.
For lab notes, record temperature, permeability ratios, and all concentrations. The CSV export keeps a tidy parameter list, and the PDF summary is useful for attaching to reports or sharing with collaborators.
It estimates membrane voltage from ion concentrations and relative permeabilities, typically for K⁺, Na⁺, and Cl⁻ in resting conditions.
Chloride carries negative charge. The equation accounts for this by using intracellular chloride in the numerator and extracellular chloride in the denominator.
No. Relative ratios are sufficient. Many models set Pk to 1 and scale Pna and Pcl relative to potassium permeability.
Use the temperature of the preparation or environment. For human physiology, 37 °C is common; experimental setups may be lower.
Large magnitude can come from extreme gradients, very small denominators, or unrealistic permeabilities. Recheck concentration units and ensure all values are positive.
No. Nernst applies to one ion at equilibrium. Goldman combines multiple ions and permeabilities to approximate the overall membrane voltage.
This calculator focuses on K⁺, Na⁺, and Cl⁻. To include additional ions, you would extend the numerator and denominator with their permeability-weighted terms.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.