Calculator
All fields accept decimals. Use consistent, realistic values.
Example data table
These sample entries illustrate typical magnitudes and outputs.
| Method | Inputs (selected units) | Lambda | Attenuation example |
|---|---|---|---|
| Specific | Radius = 5 µm, Rm = 1 kΩ·cm², Ri = 100 Ω·cm | 500 µm (0.5 mm) | At x = 1 mm → V(x)/V0 ≈ 0.1353 |
| Specific | Radius = 1 µm, Rm = 2 kΩ·cm², Ri = 120 Ω·cm | ≈ 204 µm | At x = 300 µm → V(x)/V0 ≈ 0.229 |
| Per-length | r_m = 8.0e7 Ω·m, r_i = 3.2e11 Ω/m | 500 µm | At x = 1 mm → V(x)/V0 ≈ 0.1353 |
Formula used
The cable length constant λ (also called the space constant) describes how voltage decays with distance in a passive, uniform cable.
- Specific resistances (cylinder): λ = √( a·Rm / (2·Ri) )
- Per-unit-length resistances: λ = √( r_m / r_i )
- Attenuation (optional): V(x)/V0 = exp(−x/λ)
Notes: This calculator assumes a passive, linear membrane and a uniform cable. Real neurons can deviate due to branching, active channels, and non-uniform geometry.
How to use this calculator
- Choose a method based on the parameters you have.
- Enter the required values and select the correct units beside each input.
- Optionally provide a distance x to compute V(x)/V0.
- Pick an output unit and precision, then press Calculate.
- Use the CSV/PDF buttons (shown after a result) to export.