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Cable Size

Calculate the minimum copper and aluminium wire size (AWG/MCM) based on voltage drop and ampacity.

The diameter, cross-sectional area, and electrical capacity of cables used in electrical and electronic systems are referred to as cable size. It includes elements that define the cable's fitness for a certain application, like insulation type, conductor material, and current-carrying capability.

Ensuring the safe and effective transfer of electrical power within a system is the main goal of cable sizing. A properly chosen cable size maximizes energy economy and system performance while minimizing the risk of overheating, voltage drop, and electrical problems.

Applications

Building Wiring
Industrial Installations
Automotive Wiring
Telecommunications

About This Calculator

This online electrical calculator helps find the gauge or size of copper or aluminum wires needed for an electrical circuit.

Understanding Cable Size

There are a number of things to take into account when choosing the right cable size for your particular application:

Factor	Description
Cable Bundling	When many conductors are bundled together, each conductor's ampacity must be derated, impacting total wire size requirements
Frequency of Operation	The skin effect in AC applications can alter wire sizing and effective resistance depending on operating frequency
Resistance	All conductors have some resistance — inversely proportional to diameter and directly proportional to length
Voltage Drop	Loss of electrical potential along a cable run; in Singapore, voltage drop cannot exceed 4% of the supplied voltage
Ampacity	A cable's maximum current-carrying capacity must support the maximum current that the circuit requires

Additional Considerations

Consideration	Description
Building Regulations	Familiarize yourself with local construction codes such as BS7671 in the UK to ensure adherence to electrical safety standards
Certification	Consult with a licensed electrician to ensure work is completed and certified in accordance with the necessary requirements
Cable Types	Consider insulation, conductor type, and ambient conditions when selecting the right kind of cable for your purpose

Formulas

Single Phase

$W_{CM} = \frac{2 \times K \times I \times D}{VD / SV}$

Three Phase

$W_{CM} = \frac{2 \times 0.866 \times K \times I \times D}{VD / SV}$

where:

$W_{CM}$ = Wire Circular Mils
$K$ = Specific Resistance — $11.2$ for Copper, $17.4$ for Aluminium
$I$ = Current in Amperes
$D$ = Distance
$VD$ = Voltage Drop
$SV$ = Source Voltage

Inputs

Source Voltage(V)

Supply voltage — 120, 240, or 480 volts

Number of Phases (1 = single, 3 = three)

Enter 1 for single-phase or 3 for three-phase

Amperes(A)

Load current in amps

Distance

One-way cable run distance

Distance Unit Multiplier

Unit multiplier to convert distance to feet — mm: 10, cm: 1, dm: 0.1, m: 0.01, km: 0.00001, in: 0.3937007874016, ft: 0.03280839895013, yd: 0.01093613298338

Voltage Drop(V)

Maximum allowable voltage drop in volts

Results

Copper Wire SizeInvalid ResultMinimum recommended copper wire size (AWG or MCM)

Aluminium Wire SizeInvalid ResultMinimum recommended aluminium wire size (AWG or MCM)