Electrical Conductance Calculator

About the Electrical Conductance Calculator

The Electrical Conductance Calculator computes conductance (G), conductivity (σ), and resistivity (ρ) for conductors of various materials and geometries. Conductance is the reciprocal of resistance — it measures how easily current flows through a material and is measured in siemens (S). That makes it a useful companion to resistance when you are comparing conductors by practical current flow. It is especially handy when you want to compare a conductor's performance without rewriting everything in terms of ohms. The same framework also makes it easier to compare wire sizes, materials, and temperature effects on a single page, especially when you are reviewing busbars, cable runs, or winding choices.

Conductance depends on the material's conductivity, the conductor's cross-sectional area, and its length. Copper, aluminum, silver, and gold are the most conductive metals. At the system level, conductance simplifies parallel circuit analysis — parallel conductances add directly, unlike resistances which require reciprocal addition.

Enter conductor dimensions and material properties to calculate conductance, resistance, and compare with other materials. The calculator includes a comprehensive materials database with %IACS conductivity ratings (International Annealed Copper Standard).

When This Page Helps

Use this calculator when you need to compare materials or wire sizes by how easily they carry current, not just by resistance alone. It is useful for conductor selection, temperature correction, and parallel-circuit analysis where conductance is the cleaner way to think about the problem. It also makes unit conversions between resistivity and conductivity less error-prone, which helps when you are comparing multiple conductors on the same basis.

How to Use the Inputs

1. Select the conductor material from the dropdown.
2. Enter the conductor length.
3. Enter the cross-sectional area (or use wire gauge selection).
4. Review conductance, resistance, and per-unit values.
5. Optionally enter operating temperature for temperature correction.
6. Compare conductance across materials in the reference table.

Example Calculation

Tips & Best Practices

• For power transmission, aluminum is preferred over copper due to lower cost per unit conductance.
• Stranded wire has slightly higher resistance than solid wire of the same gauge due to fill factor.
• At high frequencies (>100 kHz), skin effect reduces the effective conductor area significantly.
• Superconductors have infinite conductance (zero resistance) below their critical temperature.
• Alloys generally have lower conductivity than pure metals — brass is only 26% IACS vs copper at 100%.

Material Conductivity Reference

Common conductor materials and their approximate conductivity at 20°C: Silver: 6.30×10⁷ S/m (108% IACS). Copper (annealed): 5.80×10⁷ S/m (100% IACS). Gold: 4.11×10⁷ S/m (70.7% IACS). Aluminum: 3.50×10⁷ S/m (61% IACS). Brass: 1.59×10⁷ S/m (26% IACS). Iron: 1.04×10⁷ S/m (17.6% IACS). Stainless Steel 304: 1.39×10⁶ S/m (2.4% IACS). Nichrome: 9.09×10⁵ S/m (1.5% IACS).

The vast range of conductivity — from 6×10⁷ for silver to 10⁻¹⁴ for glass — spans over 20 orders of magnitude, making it one of the widest-ranging physical properties.

Temperature Effects on Conductance

Metal conductance decreases with temperature because lattice vibrations scatter conduction electrons. The linear approximation G(T) = G₂₀ / [1 + α(T-20)] works well from -50°C to +200°C. Temperature coefficients: copper α = 0.00393/°C, aluminum α = 0.00429/°C, iron α = 0.00651/°C. Note that semiconductors show the opposite behavior — their conductance increases with temperature as more electrons gain enough energy to enter the conduction band.

Applications in Circuit Analysis

Conductance simplifies many circuit problems. In nodal analysis, the conductance matrix (G matrix) is symmetric positive definite, making it computationally efficient. Power dissipation through a conductance: P = V²G = I²/G. Thermal conductance (watts per kelvin) is analogous — Fourier's law of heat conduction has the same mathematical form as Ohm's law.

Frequently Asked Questions

• What is the difference between conductance and conductivity?

  Conductivity (σ, measured in S/m) is a material property — it doesn't change with size or shape. Conductance (G, measured in siemens) depends on both the material and geometry (area and length). Conductance = Conductivity × Area / Length. That is why a short thick wire can conduct much better than a long thin one of the same material.

• What is %IACS?

  %IACS (International Annealed Copper Standard) expresses conductivity relative to annealed copper. 100% IACS = 5.80×10⁷ S/m. Silver is about 105% IACS. Aluminum is 61% IACS. This standard was set in 1913 and is still used today, so it is a quick way to compare metals in the same frame of reference. In practice, it gives you a consistent benchmark for wire and busbar comparisons.

• Why does resistance increase with temperature?

  In metals, higher temperature increases lattice vibrations, causing more collisions between conduction electrons and atoms. The temperature coefficient α is positive for metals (resistance increases). For copper, α ≈ 0.00393/°C — a 100°C rise increases resistance by about 39%. That is why hot conductors carry current less efficiently than the same conductor at room temperature.

• How do parallel conductances combine?

  Parallel conductances simply add: G_total = G₁ + G₂ + G₃ + ... This is one advantage of working with conductance rather than resistance for parallel circuits, where you'd need 1/R_total = 1/R₁ + 1/R₂ + ...

• What is the most conductive material?

  Silver is the most electrically conductive element at 6.30×10⁷ S/m (108% IACS). Copper is second at 5.96×10⁷ S/m (103% IACS for pure copper). Gold is third at 4.11×10⁷ S/m (70% IACS). However, copper is preferred because it's 100× cheaper than silver. In practice, cost and corrosion resistance usually matter more than the absolute ranking.

• What units is conductance measured in?

  The SI unit is the siemens (S), named after Ernst Werner von Siemens. The older unit "mho" (ohm spelled backward, symbol ℧) is exactly equivalent: 1 S = 1 mho. Millisiemens (mS) and microsiemens (µS) are common for smaller values, especially when you are working with small signal paths or high-resistance materials.