Conductance Calculator

A conductance calculator converts a known Resistance value into Conductance, expressed in siemens (S). The result is the reciprocal of resistance: a 10-ohm resistance has a conductance of 0.1 S.

Conductance is useful when evaluating parallel electrical paths. Resistance values in parallel do not add directly, but conductance values do. This makes conductance a practical intermediate value for branch-circuit analysis, parallel conductor paths, shunt networks, bonding-path evaluation, and other basic circuit calculations. For a complete branch-by-branch comparison, continue with the Parallel Circuit Calculator.

Resistance and Conductance

Resistance describes opposition to current flow and is measured in ohms (Ω). Conductance describes how readily a circuit or component permits current flow and is measured in siemens (S).

The relationship is inverse:

\(\displaystyle G = \frac{1}{R}\)

Where:

Symbol	Description	Unit
(G)	Conductance	siemens (S)
(R)	Resistance	ohms (Ω)

A lower resistance produces higher conductance. A higher resistance produces lower conductance.

For example, a 1-ohm path has a conductance of 1 S, while a 100-ohm path has a conductance of 0.01 S.

Calculator Inputs and Result

Enter the measured, specified, or calculated circuit value in the Resistance field.

Field	Electrical meaning
Resistance	The resistance of one circuit path, component, conductor, or network section, in ohms
Conductance	The reciprocal of the entered resistance, in siemens

The Resistance input must be a positive value. Zero ohms cannot be converted because its reciprocal is undefined. Negative resistance is not applicable to ordinary passive conductor and component resistance calculations.

Conductance Formula

The calculator applies:

\(\displaystyle \text{Conductance} = \frac{1}{\text{Resistance}}\)

For parallel circuit work, individual branch conductances can be added:

\(\displaystyle G_T = G_1 + G_2 + G_3 + \dots\)

The equivalent resistance of the complete parallel network is then:

\(\displaystyle R_T = \frac{1}{G_T}\)

This approach is often cleaner than repeatedly applying the reciprocal-resistance parallel formula, especially where several branches are involved.

Calculation Example

Enter the following value:

Input	Value
Resistance	10 ohm

Calculation:

\(\displaystyle G = \frac{1}{10}\)

\(\displaystyle G = 0.1\text{ S}\)

Result: Conductance = 0.1 S

If a second parallel branch also has 10 ohms of resistance, each branch has 0.1 S of conductance:

\(\displaystyle G_T = 0.1 + 0.1 = 0.2\text{ S}\)

\(\displaystyle R_T = \frac{1}{0.2} = 5\text{ ohm}\)

Two equal 10-ohm parallel paths therefore produce an equivalent resistance of 5 ohms.

Electrical Applications

Conductance is primarily used for circuit arithmetic rather than direct conductor installation sizing. Common applications include:

• Combining resistive branches in parallel circuits.
• Reviewing parallel loads, shunt resistors, and control-circuit networks.
• Converting conductor resistance into a form that can be added across parallel paths.
• Evaluating the effect of multiple metallic paths in a low-voltage or DC circuit model.
• Supporting voltage-drop calculations after individual conductor or circuit-path resistance has been established.

For conductor work, resistance may be derived from conductor material, AWG or kcmil size, conductor length, temperature, and connection conditions. Those values must be established separately. The calculation converts a known Resistance value into its reciprocal conductance.

Field and Code Limits

Conductance is not an ampacity value. It does not establish conductor size, overcurrent protection, raceway fill, adjustment factor, correction factor, terminal rating, insulation temperature rating, or voltage-drop compliance.

For installed wiring, resistance can change with conductor temperature, splice quality, termination condition, corrosion, and actual conductor length. Parallel conductors also require separate verification of installation requirements, conductor characteristics, terminations, and applicable AHJ requirements. Use the calculated conductance for electrical arithmetic, then verify the final branch-circuit or feeder design using the applicable code rules, equipment documentation, and field conditions.

For voltage-current context, see the Ohm’s Law Calculator.