Wire Size Chart: How to Choose the Right Gauge

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Choosing the correct wire gauge is essential for both electrical safety and performance. A comprehensive wire size chart helps identify the appropriate wire diameter, current capacity, and material for your application. Whether you’re working with AC or DC circuits, this guide covers AWG to mm conversions, amp ratings, and how to calculate the right size for copper and aluminum wires.

Wire size chart - choose the right gauge

Table of Contents

Understanding Wire Sizing Standards

American Wire Gauge (AWG)

The American Wire Gauge (AWG) system is a standardized method used predominantly in North America to denote the diameter of round, solid, nonferrous, electrically conducting wire. Established in 1857, AWG assigns smaller numbers to larger diameters; for instance, 12 AWG is thicker than 18 AWG. The system ranges from 40 AWG (smallest) to 0000 (4/0) AWG (largest).

(4/0) AWG, also written as 0000 AWG, is shorthand for four aught. In the American Wire Gauge (AWG) system:

  • As the gauge number decreases, the wire diameter increases.
  • After 0 AWG (one aught), sizes continue to increase using more zeros:
    • 0 AWG = 1/0
    • 00 AWG = 2/0
    • 000 AWG = 3/0
    • 0000 AWG = 4/0 (four aught)

So, (4/0) AWG is a very large wire diameter, used for high-capacity applications like heavy industrial wiring or power distribution. It’s the largest standard size in the AWG system before transitioning to kcmil (thousand circular mils) sizing.

The AWG system is officially defined by ASTM Standard B258, which specifies the nominal diameters and cross-sectional areas for solid round wires used as electrical conductors. This standard is published by ASTM International and must be purchased to access the full technical specifications.

International Standards

Outside North America, wire sizes are typically measured in square millimeters (mm²) as per the International Electrotechnical Commission (IEC) standard 60228. This metric system categorizes wires based on their cross-sectional area, facilitating global standardization.

IEC 60228 is the official international standard that governs conductor sizes expressed in square millimeters (mm²). Published by the International Electrotechnical Commission, this standard outlines detailed specifications for conductors used in insulated cables and must be purchased for full access.

Wire Size Chart Overview

A wire size chart lists wire gauge sizes with their corresponding diameters (in mm and inches) and current-carrying capacities (in amps). These values vary based on material type and application. Here’s a reference for standard copper wires used in electronics:

AWG Wire Size Chart (Copper)

The following wire size chart contains examples of wire sizes of copper wire that may be used in electronics.

AWGDiameter (mm)Diameter (inch)Max Current (Amps)Resistance (/km)
220.6440.0253553.5
200.8120.0320733.6
181.0240.04031021.2
161.2910.05081313.3
141.6280.064115–208.36
122.0530.080820–255.27
102.5880.101930–353.31

Aluminum Wire Size Chart

Aluminum wires have higher resistance than copper and require a larger gauge for the same ampacity. Here is an aluminium wire size chart for common applications:

AWGDiameter (mm)Max Current (Amps)
122.0520
102.5925–30
83.2635–40
64.1155–60
45.1970–85

Wire Sizes in Light Current Electronics

In electronics, especially in prototyping and microcontroller projects, selecting the correct wire gauge ensures signal integrity and prevents overheating.

  • 22–24 AWG: Ideal for breadboarding and jumper wires; fits snugly into standard breadboard holes and can handle currents up to a few amps. Be sure to use wire with a single solid core for breadboards.
  • 26–30 AWG: Used for signal wiring, such as in ribbon cables or internal connections within devices.
  • 18–20 AWG: Suitable for low-power applications like LED strips or small motors.

Wire Sizes in Household Electrical Wiring

Residential wiring requires adherence to safety standards and building codes, with wire sizes chosen based on the circuit’s amperage.

  • 14 AWG: Commonly used for lighting circuits protected by 15-amp breakers.
  • 12 AWG: Used for general-purpose outlets on 20-amp circuits.
  • 10 AWG: Employed for appliances like water heaters and air conditioners on 30-amp circuits.
  • 8 AWG and larger: Reserved for high-power appliances such as electric ranges or subpanels.

Wire Sizes in Industrial and Heavy Electrical Applications

Industrial settings demand wires that can handle higher currents and harsher environments.

  • 6–4 AWG: Used for large motors and heavy machinery.
  • 2–1/0 AWG: Suitable for feeder wires and large HVAC systems.
  • 2/0–4/0 AWG: Employed in heavy-duty applications like industrial power distribution and large service entrances.

Wire Sizes in Power Distribution and Data Centers

Data centers and power distribution systems require cables that ensure minimal voltage drop and can handle substantial loads.

  • 1/0–750 MCM (kcmil): Used for main power feeds and large-scale power distribution.
  • CAT5e/CAT6 (24–22 AWG): Standard for Ethernet cabling in data centers.
  • Fiber Optic Cables: While not measured in AWG, they are essential for high-speed data transmission.

Comprehensive Ampacity and Wire Size Chart

Below is an enhanced ampacity chart for both copper and aluminum conductors.

Wire Gauge / SizeDiameter (mm)Diameter (inches)Copper Ampacity (75°C / 167°F)Aluminum Ampacity (75°C / 167°F)Typical UsesVoltage Drop (V/100 ft @ 20A)
22 AWG0.6440.02537 A—Small electronics, signal wiring1.33 V
20 AWG0.8120.03211 A—Low power circuits, control wiring0.85 V
18 AWG1.0240.040316 A—Small power cords, lighting0.54 V
16 AWG1.2910.050822 A—Household appliances, low voltage0.34 V
14 AWG1.6280.06420 A—Lighting circuits, outlets0.52 V
12 AWG2.0530.08125 A20 AGeneral purpose circuits0.33 V
10 AWG2.5880.10235 A30 ASmall appliances, branch circuits0.21 V
8 AWG3.2640.12850 A40 ASubpanels, HVAC equipment0.13 V
6 AWG4.1150.16265 A50 ALarge appliances, feeders0.08 V
4 AWG5.1890.20485 A65 AMain panels, large loads0.05 V
3 AWG5.8270.229100 A75 ALarger motors, feeders0.04 V
2 AWG6.5440.258115 A90 ALarge motors, service entrance0.03 V
1 AWG7.3480.289130 A100 ASubfeeders, commercial circuits0.025 V
1/0 AWG8.2510.325150 A120 ASubfeeders, large commercial loads0.02 V
2/0 AWG9.2660.365175 A135 ALarge commercial loads0.015 V
3/0 AWG10.4040.410200 A155 AIndustrial feeders0.012 V
4/0 AWG11.6840.460230 A180 ALarge feeders, industrial0.01 V
250 kcmil13.2990.523255 A205 AVery large feeders, industrial0.008 V
300 kcmil14.7960.582285 A230 AIndustrial power distribution0.007 V
350 kcmil16.0670.633310 A250 AHeavy industrial loads0.006 V
400 kcmil17.2360.678335 A270 ALarge industrial feeders0.005 V
500 kcmil19.8120.780380 A310 AMajor industrial power distribution0.004 V
600 kcmil21.1510.833420 A340 AIndustrial and commercial power0.003 V
750 kcmil23.3250.919475 A385 AHeavy industrial feeders0.003 V
1000 kcmil26.6701.05545 A445 AVery heavy industrial power0.002 V

Footnotes:

  • Ampacity assumes 75°C insulation rating (167°F) and ambient temp of 30°C (86°F).
  • Voltage drop values are approximate for copper conductor at 20A over 100 ft.
  • Aluminum voltage drop will be ~1.6 times higher due to resistivity differences.
  • For higher ambient temperatures or multiple conductors bundled, apply derating factors per NEC or manufacturer guidelines.
  • Smaller gauges (22 AWG to 16 AWG) are typically used in electronics, control circuits, and low voltage applications.
  • Large kcmil sizes are used in heavy industry, utility, and commercial power distribution.

Wire Size Chart Temperature Correction Factors

Understanding how to select the correct wire gauge for your electrical projects is essential for safety and performance. This video provides a clear explanation of NEC ampacity tables and how to apply temperature correction and derating factors to ensure your conductors handle the required current safely.

Whether you’re working with residential wiring or high-current industrial applications, mastering these principles will help you avoid overheating and meet electrical code requirements.

Calculating Wire Size for Current

When calculating wire size, consider:

  • Current draw (amps)
  • Voltage (AC or DC)
  • Length of wire run
  • Material (copper, aluminum)

General Formula (DC Circuits):

Wire Gauge = (2 x Length x Current x Resistivity) / Voltage Drop

Use a wire size amp chart to estimate the minimum gauge required, and always round up for safety.

Wire Gauge Sizes and Wire Size Chart in mm

The AWG (American Wire Gauge) system is commonly used in the U.S., but many countries use millimeter-based sizing. Here’s a quick reference for converting AWG wire to mm.

Wire Size Chart: AWG to mm Conversion

These are just a few even number samples from the 6 to 24 AWG range.

AWGDiameter (mm)
240.511
220.644
200.812
181.024
161.291
141.628
122.053
102.588
83.264
64.115

Wire Size Conversion Formula

There is a formula to convert AWG (American Wire Gauge) to the diameter in millimeters (mm).

The AWG system is logarithmic, so the conversion is based on powers of 92. The standard formula to get the diameter \( d \) in inches from AWG number \( n \) is:

\( d_{in} = 0.005 \times 92^{\frac{36 – n}{39}} \)

To convert that diameter into millimeters, multiply by 25.4 (since 1 inch = 25.4 mm):

\( d_{mm} = 0.127 \times 92^{\frac{36 – n}{39}} \)

Wire Size Conversion Formula Summary

  • \( n \) = AWG number (an integer, e.g., 12, 24, etc.)
  • dmm = wire diameter in millimeters

Formula:

\( d_{mm} = 0.127 \times 92^{\frac{36 – n}{39}} \)

Wire Size Conversion Example

For 12 AWG wire:

\( d_{mm} = 0.127 \times 92^{\frac{36 – 12}{39}} = 0.127 \times 92^{\frac{24}{39}} \approx 2.05 \text{ mm} \)

Tips for Wire Size Chart Use

  • Choose a larger gauge for long wire runs to reduce voltage drop.
  • Use copper where size constraints exist; it’s more conductive.
  • When in doubt, refer to an electrical wire size chart based on your load.
  • Always check local codes and standards.

Did You Know About Wire Size Charts?

  • The AWG system was developed in the 1850s for standardizing wire production.
  • Aluminum wire became popular during the 1960s due to copper shortages.
  • Calculating cable size for large loads often requires software or engineering tools.

Wire Size Chart Frequently Asked Questions

What is the best way to convert AWG to mm?

Use an awg wire to mm conversion chart or multiply the AWG diameter in inches by 25.4.

How do I select wire gauge based on amps?

Refer to a wire size amp chart and consider safety margins and voltage drop over the wire length.

Is copper better than aluminum for wiring?

Copper offers better conductivity and is preferred for electronics. Aluminum is lighter and cheaper but less efficient.

What’s the difference between wire gauge and diameter?

Wire gauge is a standardized numbering system, while diameter is the actual thickness of the wire.

Can I use the same chart for AC and DC wiring?

You can use the same wire gauge diameter chart, but current ratings may differ slightly due to factors like reactance in AC circuits.

Wire Size Chart Conclusion

A reliable wire size chart is an essential reference for safe and efficient electrical and electronic projects. By understanding wire gauge sizes, wire material properties, and ampacity, you can select the right wire for any job. Use the tables provided to compare AWG, mm, and amp limits across different materials like copper and aluminum.