Check Bill Online

Wire Gauge Chart (AWG) | CheckBillOnline.com

Wire Gauge Chart (AWG)

This chart provides the standard nominal diameters and cross-sectional areas of American Wire Gauge (AWG) sizes for solid round wires used as electrical conductors.

Unlike many other charts found online, all values on this page are fully compliant with ASTM B258-18 — the authoritative standard for wire gauges. Use the search box below to instantly filter by AWG size.

🔍 Search AWG Size:

Resistance Unit:

Showing all 49 AWG sizes

Size AWG	Diameter			Cross-sectional Area		Resistance for Copper Wire
Size AWG	mils	mm	inches	cmils	mm²	Ω/1000ft	Ω/km

Table 1. Standard nominal diameters and cross-sectional areas of AWG sizes of solid round wires at 20°C — ASTM B258-18 compliant. © CheckBillOnline.com

How to Use This Wire Gauge Chart

The American Wire Gauge (AWG) system is the standard method used in the United States and Canada to express the diameter of round, solid, electrically conducting wire. The AWG number works inversely — a lower AWG number means a thicker wire, while a higher AWG number means a thinner wire. For example, a 4/0 (pronounced "four-ought") wire is much thicker than a gauge-22 wire.

This chart is your one-stop reference for all key electrical properties of AWG wire sizes, from the thickest 4/0 down to the ultra-fine gauge 45. Here's how to read and use each column:

AWG Size: The American Wire Gauge number. Sizes with "/0" (like 4/0, 3/0, 2/0, 1/0) represent very thick wires used in heavy-duty power distribution.
Diameter (mils, mm, inches): The physical width of the bare wire. Use millimetres (mm) for metric work, mils or inches for imperial measurements. 1 mil = 0.001 inch.
Cross-sectional Area (cmils & mm²): The area of the wire's circular cross-section. Circular mils (cmils) are the traditional US measure; mm² is the metric equivalent used in international standards.
Resistance (Ω/1000ft & Ω/km): The electrical resistance per unit length of solid copper wire at 20°C. Lower resistance means the wire can carry more current over longer distances without significant voltage drop.

Step-by-Step Instructions

Step 1 — Search: Type an AWG number (e.g. "12" or "4/0") into the search box to instantly highlight and filter the table to that gauge.
Step 2 — Read Diameter: Find the wire's diameter in your preferred unit — mils, mm, or inches.
Step 3 — Read Cross-section: Note the cross-sectional area in cmils or mm² for ampacity and code compliance checks.
Step 4 — Check Resistance: Use the Ω/1000ft or Ω/km columns to calculate voltage drop over a cable run. Toggle between units with the button above the table.
Step 5 — Download or Print: Use the buttons above the table to save a CSV copy or print the full chart for use in the field.

Always verify wire selection against your local electrical code (NEC in the US, CEC in Canada) and consider factors like insulation type, ambient temperature, bundling, and whether the wire is run in conduit before finalising your gauge choice.

Practical Example

Scenario: You are wiring a 20-ampere circuit in a residential home using copper wire. You need to choose the correct AWG size and estimate the voltage drop over a 50-foot one-way run.

Solution:

For a 20 A circuit, NEC typically requires a minimum of AWG 12 copper wire.
From the table, AWG 12 has a resistance of 1.5886 Ω/1000ft.
Total conductor length (both ways) = 50 ft × 2 = 100 ft.
Resistance of 100 ft = (1.5886 / 1000) × 100 = 0.159 Ω.
Voltage drop = Current × Resistance = 20 A × 0.159 Ω = 3.18 V (about 2.7% on a 120 V circuit — within NEC's 3% guideline).

Parameter	Value
AWG Size	12
Diameter	2.052 mm / 0.0808 in
Cross-section	3.308 mm²
Resistance	1.5886 Ω/1000ft
100 ft loop resistance	0.159 Ω
Voltage drop @ 20 A	3.18 V (2.65%)

Frequently Asked Questions (FAQ)

What does AWG stand for? ▼

AWG stands for American Wire Gauge. It is a standardized system used in North America to define the diameter and cross-sectional area of electrically conducting wire. The AWG system was first introduced in 1857 and remains the dominant standard for wire sizing in the US and Canada.

Why do higher AWG numbers mean thinner wire? ▼

The AWG scale is based on the number of drawing steps required to produce the wire. More drawing steps produce a thinner wire. Since it takes more passes through a die to make a thin wire, the gauge number increases as the wire gets thinner. This is counterintuitive but consistent throughout the AWG system.

What is the most common AWG wire size for household wiring? ▼

AWG 14 and AWG 12 are the most common wire sizes in US residential wiring. AWG 14 (rated for 15 A circuits) is used for general lighting and outlets, while AWG 12 (rated for 20 A circuits) is used for kitchen appliances, bathrooms, and higher-load outlets. AWG 10 is typically used for dryers, AC units, and 30 A circuits.

What is the difference between solid wire and stranded wire? ▼

This chart covers solid round wire — a single conductor. Stranded wire is made of multiple thin wires twisted together, making it more flexible. Both types are available in the same AWG sizes, but stranded wire has a slightly larger overall diameter due to air gaps between strands. The electrical resistance values in this chart apply to solid wire only.

What is ASTM B258-18 and why does it matter? ▼

ASTM B258-18 is the standard specification published by ASTM International that defines the standard nominal diameters for round solid wire for electrical conductors. All values in this chart comply fully with this standard, ensuring accuracy for use in engineering, code compliance, and procurement.

How do I convert AWG to mm²? ▼

Look up the AWG size in the chart and read the mm² column directly. For example, AWG 10 = 5.261 mm², AWG 12 = 3.308 mm², AWG 14 = 2.082 mm². Alternatively, the formula is: mm² ≈ 0.012668 × 92^((36 − AWG) / 39). The chart is the most convenient reference for standard sizes.

What is resistance per 1000 feet and how do I use it? ▼

The Ω/1000ft value tells you how much electrical resistance one thousand feet of that wire has at 20°C. To find the resistance of any length, multiply: R = (Ω/1000ft) × (length in ft / 1000). For voltage drop, multiply the result by the current in amperes: V drop = R × I. Remember to account for both the outgoing and return conductors (double the one-way run length).

Does this chart apply to aluminium wire too? ▼

The diameters and cross-sectional areas in this chart apply to both copper and aluminium wire of the same AWG size. However, the resistance values shown are for copper only. Aluminium has roughly 61% of copper's conductivity, so its resistance per unit length is approximately 1.64× higher. For aluminium resistance, multiply the copper values by approximately 1.64.

Can I use this tool for free? ▼

Yes! This tool is completely free to use on CheckBillOnline.com. You can search, filter, print, and download the data at no cost. All values are accurate and ASTM-compliant. Please do not copy or reproduce this tool's code or content on other websites.

OVER VIEW

CheckBillOnline is your one-stop digital platform for instantly checking and managing all your bills – electricity, gas, water, and internet – from a single convenient location.