NEC Wire Size in AWG Calculator for Copper and Aluminum

Copper and Aluminum Wire and Cable Size in AWG Calculator – NEC

There are multiple factors affecting wire size, including current carrying capacity, voltage drop, ambient temperatures, conductor material, frequency, cable bundling, installation type and method, load type, and local area codes (e.g., NEC and IEC).

If you are familiar with basic electrical calculations and tables, you can manually determine the appropriate wire size for electrical wiring installations in both imperial and metric systems using solved examples and reference tables. Alternatively, you can use the following NEC wire size in AWG calculator to perform the same task more quickly and efficiently for wire and cable sizing.

• Related Post: Cable and Wire Size Calculator – Copper and Aluminum) in AWG (American Wire Gauge)

Calculating Wire/Cable Size formula for single Phase Circuits

Wire Circular mils = 2 x ρ x I x L / (%Allowable Voltage drop of source voltage)

Calculating Wire/Cable Size formula for Three Phase Circuits

Wire Circular mils = √3 x 2 x ρ x I x L / (%Allowable Voltage drop of source voltage)

Where;

• ρ = Specific resistance or resistivity of Conductor
• D = Distance in Feet (One way) i.e. ½ the total circuit length
• I = Load Current

Note: the Value of ρ = Specific resistance or resistivity of Conductor is used here for copper and aluminum is 12.9 and 21.2 respectively at 75°C (167°F).

• Also check the “Good to know” Section right after the calculator

Enter value, And click on calculate. Result will show the required quantity.

Good to Know:

If the wire size is greater than all gauges (i.e 0000 is largest one size of wire in), then electrical engineer measure it in CM, kCM or MCM instead of inches, because inch is a small unit of these kinds of wires. Where;

A circular mil (CM) is a unit of circular area with a diameter of one mil (one thousandth of an inch). It corresponds to 5.067×10^-4 mm².

Where:

1000 CM (circular mils) = 1 MCM or 1 kcmil = 0.5067 mm², so 2 kcmil.

It is a unit for referring to the area of a wire with a circular cross section.

Notes:

• This wire size calculator is based on NEC Table 310.16 for both copper and aluminum in AWG at 60°C, 75°C and 90°C temperature. 
• NEC recommends ≤3% voltage drop for branch circuits and ≤5% total.
• The factor of 1.25 is added for continuous load (which lasts longer than 3 hours e.g. lighting points) and non-continuous (runs less than 3 hours) are given as per NEC 210.19(A) and 210.20(A).
• Always verify with latest NEC tables, derating factors, and a licensed electrician.

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