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Complete AWG Wire Size Chart & Reference Guide

American Wire Gauge (AWG) comprehensive reference table with diameters, resistance, ampacity ratings, and metric conversions for electrical installations.

Wire Size Calculator NEC Table 310.16

Quick AWG Reference - Most Common Sizes

14 AWG

• Diameter: 1.628 mm
• 15A circuits
• Lighting & outlets

12 AWG

• Diameter: 2.053 mm
• 20A circuits
• Kitchen & bathroom

10 AWG

• Diameter: 2.588 mm
• 30A circuits
• Dryers & A/C

6 AWG

• Diameter: 4.116 mm
• 60A circuits
• EV chargers

Complete AWG Wire Size Table

AWG	Diameter (mm)	Diameter (inch)	Area (mm²)	Resistance (Ω/1000ft)	Cu Ampacity 75°C	Al Ampacity 75°C
18	1.024	0.0403	0.823	6.385	—	—
16	1.291	0.0508	1.310	4.016	—	—
14	1.628	0.0641	2.08	2.525	20*	—
12	2.052	0.0808	3.31	1.588	25*	20*
10	2.588	0.1019	5.26	0.999	35*	30*
8	3.264	0.1285	8.37	0.628	50	40
6	4.115	0.1620	13.30	0.395	65	50
4	5.189	0.2043	21.20	0.249	85	65
3	5.827	0.2294	26.70	0.197	100	75
2	6.543	0.2576	33.60	0.156	115	90
1	7.348	0.2893	42.40	0.124	130	100
1/0	8.255	0.3250	53.50	0.0983	150	120
2/0	9.266	0.3648	67.40	0.0779	175	135
3/0	10.404	0.4096	85.00	0.0618	200	155
4/0	11.684	0.4600	107.00	0.0490	230	180

* Limited by NEC 240.4(D) small conductor rule. 14 AWG max 15A, 12 AWG max 20A, 10 AWG max 30A protection.

AWG to Metric Wire Size Conversion

Common AWG to mm² Conversions

AWG	mm²	Nearest Metric
14 AWG	2.08	2.5 mm²
12 AWG	3.31	4 mm²
10 AWG	5.26	6 mm²
8 AWG	8.37	10 mm²
6 AWG	13.3	16 mm²
4 AWG	21.2	25 mm²
2 AWG	33.6	35 mm²
1/0 AWG	53.5	50 mm²

AWG System Explained

The AWG system is logarithmic - each 3-gauge decrease doubles the cross-sectional area.

Smaller AWG numbers = larger wire diameters. AWG 0000 (4/0) is the largest standard size.

For sizes larger than 4/0, kcmil (MCM) is used, representing thousands of circular mils.

Formula: Diameter(n) = 0.005 × 92^((36-n)/39) inches

Wire Size Selection by Application

Residential Circuits

Lighting (15A)14 AWG
Outlets (20A)12 AWG
Kitchen GFCI (20A)12 AWG
Bathroom (20A)12 AWG

Appliances

Dryer (30A)10 AWG
Range (50A)6 AWG
Water Heater (30A)10 AWG
A/C Unit (20-30A)12-10 AWG

Special Applications

EV Charger (60A)6 AWG
Hot Tub (50A)6 AWG
Sub Panel (100A)2 AWG
Service (200A)3/0 AWG

Important: These are typical sizes. Always calculate based on actual load, distance, and voltage drop. Consult NEC and local codes for specific requirements.

Wire Cost Comparison by Size

Wire Size	Copper $/ft	Aluminum $/ft	Savings %	100ft Cost Cu	100ft Cost Al
14 AWG	$0.45	—	—	$45	—
12 AWG	$0.65	$0.35	46%	$65	$35
10 AWG	$0.95	$0.45	53%	$95	$45
8 AWG	$1.55	$0.75	52%	$155	$75
6 AWG	$2.80	$1.20	57%	$280	$120
2 AWG	$5.50	$2.20	60%	$550	$220
2/0 AWG	$12.50	$4.80	62%	$1,250	$480

*Prices are approximate 2024 market averages for THHN/THWN-2 wire and may vary by location and supplier.

Technical Resources & Standards

NEC Standards

NFPA 70 - NEC
• Article 310 - Conductors
• Table 310.16 - Ampacities
• Chapter 9, Table 8 - Properties

Industry Standards

ASTM B258 - AWG Sizes
UL Wire & Cable Guide
• IEC 60228 - Metric sizes

Manufacturer Data

Related Calculators & Guides

The Math Behind AWG — ASTM B258 and the Geometric Progression

AWG is not arbitrary. The numbers in the table above derive from a specific geometric progression defined by ASTM B258 (the Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors). Understanding the math lets you derive any AWG specification from first principles.

The geometric definition

AWG is anchored at two endpoints: 0000 (4/0) AWG = 0.4600″ diameter, and 36 AWG = 0.0050″ diameter. The 38 sizes between 4/0 and 36 are spaced in a geometric progression.

Common ratio: r = (0.4600 / 0.0050)^1/39 = 92^1/39 ≈ 1.1229

Diameter formula: d_n = 0.0050 × 92^(36-n)/39 inches

Each step UP in AWG (e.g., 14 → 12) multiplies diameter by 1.1229

Each 6-step jump multiplies diameter by ~2 (a useful approximation)

Each 3-step jump multiplies area by ~2

Each 10-step jump multiplies resistance by ~10

Above 4/0 — kcmil takes over

AWG runs out at 4/0 (0.4600″). Larger conductors are specified by cross-sectional area in kcmil (thousands of circular mils). 1 circular mil = the area of a circle with diameter 0.001 inch (1 mil).

Area in cmil = (diameter in mils)²

1 kcmil = 1,000 cmil = 0.5067 mm²

Examples:

4/0 AWG ≈ 211.6 kcmil (107 mm²)

250 kcmil = 250,000 cmil (127 mm²)

500 kcmil = 500,000 cmil (253 mm²)

Older spec uses MCM (Roman M = 1,000); MCM = kcmil

AWG ↔ Metric SI conversion

Most of the world uses metric SI sizes (mm²) instead of AWG. Conversion is exact: 1 kcmil = 0.5067 mm². The table below pairs each AWG size with the closest commercial metric SI size, the conversion factor, and a note on whether the substitution is safe.

AWG	Exact area (mm²)	Closest std SI size	SI vs AWG	Substitution note
14	2.08	2.5 mm²	SI is +20%	2.5 mm² is fine for 14 AWG circuits; common in EU residential.
12	3.31	4 mm²	SI is +21%	4 mm² is the EU standard for 20 A circuits.
10	5.26	6 mm²	SI is +14%	6 mm² substitutes safely; common for EU dryers.
8	8.37	10 mm²	SI is +20%	10 mm² for cookers, water heaters in EU.
6	13.30	16 mm²	SI is +20%	16 mm² for sub-mains in EU dwellings.
4	21.15	25 mm²	SI is +18%	25 mm² for service-entrance / submains.
2	33.62	35 mm²	SI is +4%	35 mm² is closest match — same ampacity tier.
1/0	53.49	50 mm²	SI is −6%	50 mm² is slightly smaller — verify ampacity.
2/0	67.43	70 mm²	SI is +4%	70 mm² matches.
4/0	107.2	120 mm²	SI is +12%	120 mm² is the standard SI replacement for 4/0.
250 kcmil	126.7	150 mm²	SI is +18%	150 mm² runs cooler — preferred where available.
500 kcmil	253.4	240 mm²	SI is −5%	240 mm² is the closest standard size.

Note: NEC 310.16 ampacities are defined for AWG / kcmil conductors. When substituting metric SI conductors in NEC-jurisdiction work, verify the actual cross-sectional area meets or exceeds the AWG it replaces. IEC 60364 ampacity tables differ in derating philosophy from NEC.

Stranded vs solid — when each is required

All AWG diameters in the table above are for SOLID conductor. Stranded conductors of the same AWG have a slightly larger overall diameter (typically 8–15 % larger) because of the gaps between strands.

Solid: required for fixed wiring 14–10 AWG (NEC 334.10 NM-B cable). Cheaper, easier to terminate under screw lugs.
Stranded: required above 8 AWG (too stiff to bend). Required by Class B / Class C strand counts in NEC Chapter 9 Table 10. Necessary for control wiring, vibration applications.
Class B (typical building): 7 strands at small AWG, 19 strands above 1/0.
Class C / D / K (flexible): finer stranding for control cable, welding cable, portable cord.

Insulation type — pick by environment

Two conductors of identical AWG can have very different ampacities depending on insulation rating. NEC 310.16 organizes by insulation temperature class:

60°C (TW, UF): direct burial, wet locations, older NM. Lowest ampacity.
75°C (THW, THWN, RHW, USE, XHHW wet, NM-B at conductor): general-purpose; most common termination rating.
90°C (THHN, XHHW-2 dry, RHH, USE-2): highest ampacity in conduit. NM-B cable insulation is 90°C but ampacity is capped at 60°C column per NEC 334.80.

Key: the entire circuit’s ampacity is limited by the lowest-rated component. Most breakers and panels in residential service are rated 75°C, so even if you use 90°C THHN conductor, you must use the 75°C ampacity column — NEC 110.14(C).

Worked derivation — why 12 AWG is rated 25 A at 75°C

The ampacity values in NEC 310.16 are not arbitrary. They derive from a heat-balance equation between I²R losses in the conductor and convective + radiative cooling at the conductor surface, normalized to the insulation’s rated operating temperature with 30°C ambient.

12 AWG copper: diameter = 2.05 mm, surface area per ft = 0.0808″ × π × 12 = 3.05 in²

R_20°C = 1.588 Ω/1000 ft (NEC Chapter 9 Table 8)

R_75°C = R_20°C × (1 + 0.00393 × 55) = 1.588 × 1.216 = 1.93 Ω/1000 ft

At 25 A, I²R loss = 25² × 1.93 / 1000 = 1.21 W/ft

This power dissipation corresponds to a 45°C rise above ambient (with 75°C insulation, 30°C ambient → 75°C operating).

Push to 30 A: I²R = 30² × 1.93 / 1000 = 1.74 W/ft → 65°C rise → exceeds 75°C insulation rating

Hence 12 AWG @ 75°C ampacity is exactly 25 A.

Why 12 AWG ampacity is 25 A but the breaker can’t exceed 20 A

NEC 240.4(D) is the “small-conductor rule”: regardless of higher 310.16 ampacity, the OCPD on 14, 12, 10 AWG copper is capped:

14 AWG: ampacity 20 A (75°C), OCPD max 15 A
12 AWG: ampacity 25 A (75°C), OCPD max 20 A
10 AWG: ampacity 35 A (75°C), OCPD max 30 A

Why the discrepancy? Small conductors are disproportionately sensitive to mechanical damage, poor terminations, and accumulated dust. The 240.4(D) cap creates a safety margin that 8 AWG and larger conductors don’t need. There are five exceptions (motor circuits, taps, listed equipment, Air-conditioning per Article 440, fire alarm per Article 760) but they’re narrow.