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Wire Gauge Chart

Look up AWG wire gauge charts for diameter, area, and typical ampacity reference values in one place. Runs locally in your browser. Try it free.

Instant result
Result
—

Enter values to calculate.

Inputs—
Mode—
Formula—
Trust summary CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance · AWG geometry & calculation contract
Input interpretation
Enter values to calculate.
Result
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Verified scope
AWG geometry & calculation contract
Assurance
Engineering
Declared partition coverage
PASS · 5/5 declared partitions (geometry-formula, geometry-standard-nominal, copper-resistance-model, ampacity-reference-integrity, invalid-domain) · Matrix
Numerical scope
CVP numerical verification covers AWG diameter/area geometry (unrounded formula + ASTM Table 1 identity). Copper resistance is a 20 °C IACS material model. Ampacity is an educational code-context reference and is outside CVP golden numeric verification.
Known limitations
  • Core CVP does not include live graph, viewport, or pointer interaction.
Model
AWG lookup: unrounded ASTM B258 geometric progression (primary) plus Table 1 SI standard nominals for integer 4/0–56; 20 °C copper resistance (material model); educational NFPA 70–style thermal ampacity reference (table-like 310.16, edition not pinned, code context required, not a branch-circuit/OCPD rating).
Scope
CVP numerical verification covers AWG diameter/area geometry. Copper resistance is a 20 °C IACS material model. Ampacity is an educational code-context reference and is outside CVP golden numeric verification.
Verification
Engine tested · Source checked · v1.5.0 · CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance · AWG geometry & calculation contract· View Manifest · CVP overview · Specification
Versions
Calculation 1.5.0 · CVP protocol 1.0.0-proposed · Evidence 2026-09-10.wire-chart-claim-boundary
Verification revision
2026-09-10.wire-chart-claim-boundary · 5/5 property · digest 42bdfb24710d
Legacy regression
46/46 tests · Production surface contract 4/4
Reference
O1 model · O1 model · O2 expected_values · O2 numerical_behavior
Interfaces
PASS · UI (SSR) / REST / MCP — ui-ssr is query-result HTML, not a live browser session. Human URL alias: /calc/wire/wire-gauge-chart?a=12&mode=awg-mm ≡ /calc/wire/awg-to-mm?awg=12&mode=awg-mm ≡ REST awg-to-mm and wire-gauge-chart ≡ MCP electrical.awg_to_mm.
Supplemental domain review
Not performed
Named expert review
Not performed
CVP suite
6/6 golden · 5/5 CVP boundary · 6/6 invalid · 5/5 property · 2/2 cross-interface · 1/1 CVP contract · Manifest
Sources
Sources
Evidence
13 legacy golden · 6 legacy boundary · legacy regression suite · 6/6 oracle-backed golden · 6/6 invalid · Artifact integrity PASS
This calculator CURRENT · Public schema 1.5.0 matches · Semantic contract ✓ · Production attested · Public/cache ✓ · Origin ✓
Semantic contract
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Full verification

Manifest identity, reference classes, interfaces, suite, and production records.

Formulas

Core equations used by this calculator.

Diameterdₙ (mm) = 0.127 × 92^((36−n)/39)
AreaAₙ (mm²) = (π/4) × dₙ²
ResistanceR (Ω/km) = 10⁹ × ρ / Aₙ
Heavy gauges4/0, 3/0, 2/0, 1/0 (legacy −3…0)
iBy definition, AWG 36 is 0.005 in (0.127 mm) and AWG 4/0 is 0.46 in (11.68 mm) — a 92:1 diameter ratio over 39 steps. Copper Ω/km is a 20 °C material model. Ampacity columns are educational NFPA 70–style thermal references (table-like 310.16, edition not pinned) — not permitted branch-circuit ratings and not jurisdiction-usable. Always verify with the code and cable type for your installation.

How to use

1

Choose diameter or area

AWG → mm for diameter; AWG → mm² for round cross-section.

2

Enter the gauge

Type 12, 1/0, or 4/0. Legacy −3…0 still works. Ordinary gauges (1–40) are entered as written.

3

Read the lookup card

Diameter, area, 20 °C copper resistance, and thermal ampacity reference appear together — they are not the same kind of fact. Long runs also need a voltage-drop check.

Example calculations

Common configurations with formula and result.

ϟ

Household 20 A circuit

AWG 12 copper

d & area
2.0525 mm · 3.31 mm² · 20 A @ 60 °C thermal reference (not OCPD)
ϟ

Household 15 A circuit

AWG 14 copper

d & area
1.6277 mm · 2.08 mm² · 15 A @ 60 °C thermal reference (not OCPD)
ϟ

Doubling diameter

Rule of thumb

−6 AWG steps
≈ 4× area / conductance
ϟ

Doubling area

Rule of thumb

−3 AWG steps
≈ 2× conductance

Common copper sizes (quick lookup)

Common values at a glance.

AWGDiameter (mm)Area (mm²)Cu Ω/km @ 20 °C60 °C ref (A)
141.62772.08098.28615
122.05253.30885.21120
102.58825.26123.27730
83.26368.36562.06140
64.115413.30181.29655
45.189421.15060.81570
26.543733.63080.51395
1/08.251553.47510.322125
4/011.6840107.21930.161195
i 60 °C column is a copper thermal ampacity reference, not a permitted branch-circuit rating. Confirm conductor type, termination temperature, and local code (NEC 240.4(D) often limits 14/12/10 AWG copper OCPD to 15/20/30 A). Resistance is solid copper at 20 °C.

Wire Gauge Chart specification

Version 1.5.0 · Engine tested

Calculation status

Review policy · Evidence

Definition
American Wire Gauge (AWG) is a logarithmic North American standard (ASTM B258) for solid round non-ferrous wire. Smaller AWG numbers are thicker. This page combines an AWG → mm converter with diameter, area, copper resistance, and typical copper ampacity tables for quick reference.
What it calculates
AWG lookup: unrounded ASTM B258 geometric progression (primary) plus Table 1 SI standard nominals for integer 4/0–56; 20 °C copper resistance (material model); educational NFPA 70–style thermal ampacity reference (table-like 310.16, edition not pinned, code context required, not a branch-circuit/OCPD rating).
Inputs
  • AWG gauge (12, 1/0, 4/0, or legacy n = −3…40+; −3=4/0 … 0=1/0)
Outputs
  • Diameter (mm) and round area (mm² / kcmil)
  • Copper Ω/km and Ω/1000 ft at 20 °C (material model)
  • Copper thermal ampacity reference (60/75/90 °C) when tabulated
Formula
d = 0.127×92^((36−n)/39); A = (π/4)×d²
Assumptions
  • Solid round conductor for diameter/area (ASTM B258-18(2026); 2026 reapproval of B258-18).
  • Copper resistance = 20 °C, 100% IACS ρ = 1.7241×10⁻⁸ Ω·m (NBS Handbook 100).
  • Ampacity from educational NFPA 70–style copper charts (table-like 310.16); edition not pinned; no derating; not jurisdiction-usable and not a branch-circuit rating.
Units
  • mm, mm², kcmil, Ω/km, A
Boundary conditions
  • Integer AWG 4/0 (−3) through 56 is standard_range + formula_derived (+ ASTM Table 1 standard_nominal); non-integer n in that span is nonstandard_gauge (AWG_NONSTANDARD_GAUGE, formula_interpolation); n outside the span is formula_extrapolation (AWG_OUTSIDE_STANDARD_RANGE)
  • Empty/missing awg → MISSING_REQUIRED_INPUT (not coerced to 1/0)
  • Lower AWG number → thicker diameter (monotonic)
  • field=mm → primary diameter; field=mm2 → πd²/4 area (lookup always returns both)
  • Solid round conductor only — not stranded equivalent OD
  • Ampacity tables are thermal reference only; thermal ampacity ≠ permitted branch-circuit rating
Example
AWG 12 → 2.0525 mm, 3.3088 mm², 5.211 Ω/km @ 20 °C, 20/25/30 A thermal reference
Validation cases

16 published on this page · 46/46 tests · Production surface contract 4/4 · View evidence

  • AWG 36 → 0.1270 mm (by definition) / 0.0127 mm²
  • AWG −3 (4/0) → 11.6840 mm / 107.2193 mm²
  • AWG 12 → 2.0525 mm / 3.3088 mm²
  • AWG 18 → 1.0237 mm / 0.8230 mm²
  • AWG 0 (1/0) → 8.2515 mm / 53.4751 mm²
  • AWG 10 → 2.5882 mm / 5.2612 mm²
  • AWG 40 → ≈0.0799 mm
  • AWG 4/0 token → same as −3 → 11.6840 mm / 107.2193 mm²
  • AWG 1/0 token → same as 0 → 8.2515 mm / 53.4751 mm²
  • AWG 100 → finite formula result + warning AWG_OUTSIDE_STANDARD_RANGE
  • AWG 12.5 → finite interpolated diameter + warning AWG_NONSTANDARD_GAUGE (not outside-range)
  • AWG 12 mm vs mm2 consistency → mm2 = πd²/4 from mm
  • AWG 10 diameter > AWG 12 → true (thicker lower gauge)
  • AWG 36 reference → 0.127 mm exactly (scale anchor)
  • Same AWG twice → deterministic identical diameter
  • AWG 10 copper R (model) → ≈ 3.277 Ω/km (≈ 1 Ω/1000 ft) — material model at 20 °C
Sources
  • ASTM B258-18(2026) — Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors — Nominal diameters and areas for AWG sizes (PRIMARY — geometry). 2026 is a reapproval of B258-18; the AWG geometric progression is unchanged.
    Supports: d = 0.127×92^((36−n)/39); A = (π/4)×d²
  • NBS Handbook 100 — Copper Wire Tables — American Wire Gage geometric progression (No. 0000 = 0.4600 in, No. 36 = 0.0050 in, ratio 92^(1/39)); International Annealed Copper Standard volume resistivity 1.7241 μΩ·cm at 20 °C
    Supports: PRIMARY formula track: logarithmic AWG scale with d₃₆ = 0.127 mm; 100% IACS ρ = 1.7241×10⁻⁸ Ω·m
  • 100% IACS annealed copper resistivity (20 °C) — Material: annealed copper, 100% IACS; reference temperature 20 °C; ρ = 1.7241×10⁻⁸ Ω·m (NBS Handbook 100)
    Supports: Copper Ω/km from area; IACS conductivity definition. Material-model reference, not ASTM B258 geometry.
  • NFPA 70–style copper ampacity (educational; edition not pinned) — Table-like 310.16 family: copper, not more than three current-carrying conductors, no ambient or bundling correction
    Supports: Educational thermal reference only; not an adopted NFPA 70 edition or jurisdiction table; not a branch-circuit/OCPD rating
  • NIST Guide to the SI (SP 811) — Millimetre as SI length unit
    Supports: Diameter in mm; area in mm²
Calculation version
1.5.0

Background

Interpretation and common distinctions.

What is the AWG wire gauge chart?

American Wire Gauge (AWG) is the usual North American size system for round, solid, non-ferrous electrical wire. It has been used since 1857 and is specified in ASTM B258-18(2026) (2026 reapproval of B258-18). Dimensions are logarithmic: each step multiplies diameter by 92^(1/39) ≈ 1.1229.

This page is a practical wire gauge chart plus a quick AWG → mm converter:

  • Diameter (inch and mm) and area (mm² / kcmil)
  • Approximate copper resistance
  • Typical copper ampacity by insulation temperature rating
  • Rules of thumb for sizing and comparison with SWG / metric mm²

AWG formulas

Diameter

dₙ (mm) = 0.127 mm × 92^((36−n)/39)

dₙ (in) = 0.005 in × 92^((36−n)/39)

By definition: AWG 36 = 0.005 in (0.127 mm) and AWG 4/0 = 0.46 in (11.68 mm).

Heavy gauges: enter 4/0, 3/0, 2/0, or 1/0 (legacy n = −3,−2,−1,0).

Cross-section

Aₙ (mm²) = (π)/4 dₙ² ≈ 0.012668 mm² × 92^((36−n)/19.5)

Above 4/0, North American power conductors are often labeled in kcmil (thousands of circular mils), e.g. 250, 500, 1000 kcmil — not AWG numbers.

Copper resistance (approximate)

Rₙ (Ω/km) = (10^9 × ρ)/(Aₙ (mm²))

with ρ = 1.7241×10⁻⁸ Ω·m (NBS Handbook 100, 100% IACS at 20 °C). Hotter wire → higher resistance.

Rules of thumb

Change in AWG Approximate effect
−3 (e.g. 14 → 11) ≈ 2× area and conductance
−6 (e.g. 18 → 12) ≈ 2× diameter, 4× area
−10 (e.g. 24 → 14) ≈ 10× area, weight, conductance

Copper resistance memory aid:

  • 10 AWG ≈ 1 Ω / 1000 ft
  • 20 AWG ≈ 10 Ω / 1000 ft
  • 30 AWG ≈ 100 Ω / 1000 ft

Aluminum has roughly 61% of copper’s conductivity — often similar resistance to copper about two AWG sizes smaller.

How to use the converter

  1. Enter the AWG size (12, 1/0, 4/0, or legacy −3…0).
  2. Read diameter, area, and 20 °C copper resistance on the lookup card.
  3. Treat ampacity as an installation-dependent thermal reference; check voltage drop on long runs (prefilled from 20 °C Cu Ω/km).

AWG size chart (solid conductor)

Bare solid diameter and area from the AWG formulas. Copper resistance ≈ 20 °C.

AWG Diameter (in) Diameter (mm) Area (mm²) Area (kcmil) Cu Ω/km Cu Ω/1000 ft
0000 (4/0) 0.4600 11.6840 107.2193 211.6 0.1608 0.0490
000 (3/0) 0.4096 10.4049 85.0288 167.8 0.2028 0.0618
00 (2/0) 0.3648 9.2658 67.4309 133.1 0.2557 0.0779
0 (1/0) 0.3249 8.2515 53.4751 105.5 0.3224 0.0983
1 0.2893 7.3481 42.4077 83.7 0.4066 0.1239
2 0.2576 6.5437 33.6308 66.4 0.5127 0.1563
3 0.2294 5.8273 26.6705 52.6 0.6465 0.1970
4 0.2043 5.1894 21.1506 41.7 0.8152 0.2485
5 0.1819 4.6213 16.7732 33.1 1.028 0.313
6 0.1620 4.1154 13.3018 26.3 1.296 0.395
7 0.1443 3.6649 10.5488 20.8 1.634 0.498
8 0.1285 3.2636 8.3656 16.5 2.061 0.628
9 0.1144 2.9064 6.6342 13.1 2.599 0.792
10 0.1019 2.5882 5.2612 10.4 3.277 0.999
11 0.0907 2.3048 4.1723 8.23 4.132 1.26
12 0.0808 2.0525 3.3088 6.53 5.211 1.588
13 0.0720 1.8278 2.6240 5.18 6.571 2.00
14 0.0641 1.6277 2.0809 4.11 8.286 2.525
15 0.0571 1.4495 1.6502 3.26 10.45 3.18
16 0.0508 1.2908 1.3087 2.58 13.17 4.02
17 0.0453 1.1495 1.0378 2.05 16.61 5.06
18 0.0403 1.0237 0.8230 1.62 20.95 6.39
19 0.0359 0.9116 0.6527 1.29 26.42 8.05
20 0.0320 0.8118 0.5176 1.02 33.31 10.15
22 0.0253 0.6438 0.3255 0.64 52.96 16.14
24 0.0201 0.5106 0.2047 0.40 84.22 25.67
26 0.0159 0.4049 0.1288 0.25 133.9 40.8
28 0.0126 0.3211 0.0810 0.16 212.9 64.9
30 0.0100 0.2546 0.0509 0.10 338.6 103
32 0.0080 0.2019 0.0320 0.06 538.3 164
34 0.0063 0.1601 0.0201 0.04 856 261
36 0.0050 0.1270 0.0127 0.025 1361 415
40 0.0031 0.0799 0.0050 0.010 3441 1049

Copper ampacity (building wire reference)

Ampacity is the maximum continuous current a conductor can carry without exceeding its temperature rating. Values below follow common NFPA 70–style copper charts for not more than three current-carrying conductors (table-like 310.16). This page does not pin a code edition and is not an adopted NEC table. They do not include ambient correction or bundling adjustments. Temperature columns are thermal ampacity references, not a mapping of insulation type (NM-B, THHN, …) onto a number. Confirm conductor type, wiring method, termination temperature, and local code.

Thermal ampacity ≠ permitted branch-circuit rating. Small-conductor overcurrent protection (NEC 240.4(D) and similar) often limits 14/12/10 AWG copper to 15/20/30 A regardless of the 90 °C column.

AWG / kcmil Cu 60 °C reference (A) Cu 75 °C reference (A) Cu 90 °C reference (A) Al 75 °C reference (A) Al 90 °C reference (A)
14 15 20 25 — —
12 20 25 30 20 25
10 30 35 40 30 35
8 40 50 55 40 45
6 55 65 75 50 55
4 70 85 95 65 75
3 85 100 115 75 85
2 95 115 130 90 100
1 110 130 145 100 115
1/0 125 150 170 120 135
2/0 145 175 195 135 150
3/0 165 200 225 155 175
4/0 195 230 260 180 205
250 kcmil 215 255 290 205 230
500 kcmil 320 380 430 310 350
750 kcmil 400 475 535 385 435
1000 kcmil 455 545 615 445 500

Household tip: many 15 A general/lighting circuits use 14 AWG copper and many 20 A receptacles use 12 AWG because of small-conductor overcurrent rules and 60 °C terminations — not because the 90 °C column is a circuit rating. Always match breaker, receptacle, and conductor ratings.

Rough load estimate: add device watts, divide by voltage (120 V or 240 V) → amps, then choose a size that meets ampacity and voltage drop.

Solid vs stranded

  • Chart diameters are for solid wire.
  • Stranded AWG is based on total copper cross-section (gaps not counted).
  • With round strands, voids are often ~25% of the envelope, so overall OD is commonly ~13% larger than solid of the same AWG.
  • Stranded callouts look like 22 AWG 7/30 (seven strands of 30 AWG).

Nomenclature

Written Spoken / alternate
12 AWG “twelve gauge”, #12, No. 12
1/0 (0) “one-aught”
2/0 (00) “two-aught”
3/0 (000) “three-aught”
4/0 (0000) “four-aught”

AWG vs other systems

System Where used Basis
AWG North America Logarithmic diameter steps
SWG UK / Imperial Separate fixed table
mm² (IEC 60228) Most of the world Direct cross-section

Use AWG to mm and SWG to mm — do not mix gauge numbers across systems.

Other calculators in this family: AWG to mm, SWG to mm, Voltage drop .

AWG AWG to mm › SWG SWG to mm › V Voltage drop ›
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Frequently asked questions

Key distinctions behind the calculation.

What is a wire gauge chart?

It is a lookup table of AWG sizes versus diameter, cross-section, and often resistance or ampacity. AWG has been used since 1857 for round solid non-ferrous conductors (ASTM B258).

Does a larger AWG mean a thicker wire?

No. Larger AWG numbers are thinner. AWG 10 is thicker than AWG 18; 4/0 is thicker than 1/0.

How do I enter 4/0, 3/0, 2/0, or 1/0?

Type 4/0, 3/0, 2/0, or 1/0. Charts also show 0000/000/00/0. Legacy numeric codes −3…0 still work.

Solid vs stranded — which diameter is listed?

Chart diameters are for solid round wire. Stranded AWG matches the equivalent copper area; the overall OD is larger (~13% is a common rule of thumb) because of gaps between strands.

What is ampacity?

Ampacity is the maximum continuous current a conductor can carry under stated conditions without exceeding its temperature rating. It depends on insulation type, ambient temperature, bundling, and code rules — not diameter alone.

Are the ampacity values code-legal for my job?

No. They are educational NFPA 70–style copper thermal references (table-like 310.16) with no code edition pinned and no correction factors. They are not jurisdiction-usable. Thermal ampacity is not the same as a permitted branch-circuit rating (NEC 240.4(D) often limits 14/12/10 AWG copper OCPD to 15/20/30 A). Confirm with the current NEC or local code, cable type, and a qualified electrician or engineer.

AWG vs SWG vs mm²?

AWG is North American; SWG is British Imperial; most of the world specifies conductors directly in mm² (IEC 60228). Same number ≠ same size across systems.

What are useful rules of thumb?

Every −3 AWG ≈ double the area; every −6 AWG ≈ double the diameter (≈4× area). Copper ≈ 1 Ω/1000 ft at 10 AWG, 10 Ω/1000 ft at 20 AWG, 100 Ω/1000 ft at 30 AWG.