WIRE GAUGE REFERENCE TOOL
Wire Gauge Chart
This wire gauge chart covers both AWG and SWG standards — look up any gauge number and get diameter (inches and mm), cross‑sectional area, resistance (Ω/1,000 ft), weight, and ampacity. Use the reverse lookup to enter a measured diameter and find the nearest AWG and SWG gauge.
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AWG & SWG conversion · 40+ gauge sizes
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Reverse lookup by diameter (in / mm)
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Wire EDM gauges (0.1–0.3 mm) highlighted
AWG & SWG Standards
Diameter · Area · Resistance · Ampacity
AWG
American Wire Gauge
SWG
British Standard Wire Gauge
mm²
IEC 60228 Cross‑section
EDM
0.1–0.3 mm highlighted
AWG to mm² Converter
AWG → mm² (IEC 60228) Essential for European cable specifications
WIRE GAUGE GUIDE
How to Use This Wire Gauge Chart
Look up by gauge number, identify unknown wire by diameter, get ampacity for your application scenario, and compare across international standards — all in five simple steps.
1. Know your gauge number? Enter it in the lookup — select AWG or SWG. You will see diameter, area, resistance, weight, and ampacity for that gauge.
2. Have an unknown wire? Measure the diameter with calipers or a micrometer and use the reverse lookup to find the nearest AWG and SWG gauge numbers.
Select Ampacity Scenario
3. Need ampacity? Choose your application: Chassis wiring (single wire in free air, higher rating) or Power transmission (bundled in conduit, lower rating). Ampacity values update to match your scenario.
Compare AWG & SWG
4. Working internationally? Use the AWG ↔ SWG comparison table to verify specs with overseas suppliers. A UK supplier quoting “10 gauge” may mean 10 SWG (3.25 mm), not 10 AWG (2.59 mm) — always confirm.
Specify Both Gauge & Diameter
5. Always write diameter in mm alongside the gauge number on purchase orders. Example: “12 AWG solid copper wire, 2.05 mm diameter, per ASTM B258.” This single habit prevents the most common wire gauge specification error.
WIRE GAUGE REFERENCE TABLE
AWG Wire Gauge Reference Table — American Wire Gauge (B&S)
Complete AWG reference for solid copper wire: diameter, cross‑sectional area, resistance per 1,000 ft at 20°C, weight, and ampacity under chassis wiring and power transmission scenarios at 75°C insulation rating.
AWG standard covers 4/0 (11.684 mm) to 40 AWG (0.079 mm). For aluminum wire, multiply resistance by 1.63 and weight by 0.30 — higher resistance, lower weight. For stranded wire, consult the stranded wire calculator section. Ampacity values are for reference; actual capacity depends on insulation, ambient temperature, bundling, and local codes. Consult the NEC (NFPA 70) for electrical installations.
| AWG | Dia (in / mm) | Area (mm²) | Ω/1,000 ft (Cu) | lb/1,000 ft (Cu) | Chassis (75°C) | Transmission (75°C) |
|---|---|---|---|---|---|---|
| 4/0 | 0.4600 / 11.684 | 107.0 | 0.0490 | 329.0 | 380 | 230 |
| 3/0 | 0.4096 / 10.404 | 85.0 | 0.0618 | 260.0 | 328 | 200 |
| 2/0 | 0.3648 / 9.266 | 67.4 | 0.0779 | 206.0 | 283 | 175 |
| 1/0 | 0.3249 / 8.252 | 53.5 | 0.0983 | 163.0 | 245 | 150 |
| 1 | 0.2893 / 7.348 | 42.4 | 0.1240 | 129.0 | 211 | 130 |
| 2 | 0.2576 / 6.544 | 33.6 | 0.1563 | 102.0 | 181 | 115 |
| 3 | 0.2294 / 5.827 | 26.7 | 0.1970 | 81.5 | 158 | 100 |
| 4 | 0.2043 / 5.189 | 21.2 | 0.2485 | 64.7 | 135 | 85 |
| 5 | 0.1819 / 4.621 | 16.8 | 0.3133 | 51.3 | 118 | 75 |
| 6 | 0.1620 / 4.115 | 13.3 | 0.3951 | 40.7 | 101 | 65 |
| 7 | 0.1443 / 3.665 | 10.5 | 0.4982 | 32.3 | 89 | 57 |
| 8 | 0.1285 / 3.264 | 8.37 | 0.6282 | 25.6 | 73 | 50 |
| 9 | 0.1144 / 2.906 | 6.63 | 0.7921 | 20.3 | 64 | 42 |
| 10 | 0.1019 / 2.588 | 5.26 | 0.9989 | 16.1 | 55 | 37 |
| 11 | 0.0907 / 2.304 | 4.17 | 1.260 | 12.7 | 47 | 32 |
| 12 | 0.0808 / 2.053 | 3.31 | 1.588 | 10.1 | 41 | 27 |
| 13 | 0.0720 / 1.828 | 2.62 | 2.003 | 8.02 | 35 | 23 |
| 14 | 0.0641 / 1.628 | 2.08 | 2.525 | 6.36 | 30 | 20 |
| 15 | 0.0571 / 1.450 | 1.65 | 3.184 | 5.05 | 26 | 17 |
| 16 | 0.0508 / 1.291 | 1.31 | 4.016 | 4.00 | 22 | 14 |
| 17 | 0.0453 / 1.150 | 1.04 | 5.064 | 3.17 | 19 | 12 |
| 18 | 0.0403 / 1.024 | 0.823 | 6.385 | 2.52 | 16 | 10 |
| 19 | 0.0359 / 0.912 | 0.653 | 8.051 | 1.99 | 14 | 9 |
| 20 | 0.0320 / 0.812 | 0.518 | 10.15 | 1.58 | 11 | 7 |
| 21 | 0.0285 / 0.723 | 0.410 | 12.80 | 1.25 | 9 | 6 |
| 22 | 0.0253 / 0.644 | 0.326 | 16.14 | 0.995 | 7 | 5 |
| 23 | 0.0226 / 0.573 | 0.258 | 20.36 | 0.789 | — | — |
| 24 | 0.0201 / 0.511 | 0.205 | 25.67 | 0.626 | — | — |
| 25 | 0.0179 / 0.455 | 0.162 | 32.37 | 0.497 | — | — |
| 26 | 0.0159 / 0.405 | 0.129 | 40.81 | 0.394 | — | — |
| 27 | 0.0142 / 0.361 | 0.102 | 51.47 | 0.312 | — | — |
| 28 | 0.0126 / 0.321 | 0.0810 | 64.90 | 0.248 | — | — |
| 29 | 0.0113 / 0.286 | 0.0642 | 81.84 | 0.197 | — | — |
| 30 | 0.0100 / 0.255 | 0.0509 | 103.2 | 0.156 | — | — |
| 31 | 0.00893 / 0.227 | 0.0404 | 130.1 | 0.124 | — | — |
| 32 | 0.00795 / 0.202 | 0.0320 | 164.1 | 0.098 | — | — |
| 33 | 0.00708 / 0.180 | 0.0254 | 206.9 | 0.078 | — | — |
| 34 | 0.00631 / 0.160 | 0.0201 | 260.9 | 0.062 | — | — |
| 35 | 0.00562 / 0.143 | 0.0160 | 329.0 | 0.049 | — | — |
| 36 | 0.00500 / 0.127 | 0.0127 | 414.8 | 0.039 | — | — |
| 37 | 0.00445 / 0.113 | 0.0100 | 523.1 | 0.031 | — | — |
| 38 | 0.00397 / 0.101 | 0.00797 | 659.6 | 0.024 | — | — |
| 39 | 0.00353 / 0.0897 | 0.00632 | 831.8 | 0.019 | — | — |
| 40 | 0.00314 / 0.0799 | 0.00501 | 1049 | 0.015 | — | — |
Aluminum & Stranded Wire Notes
For aluminum wire, multiply copper resistance by 1.63 and weight by 0.30 — aluminum has higher resistance but lower weight than copper. For stranded wire, use the stranded wire calculator; effective cross‑sectional area is the same as solid, but diameter and weight differ due to air gaps between strands.
Ampacity Disclaimer & NEC Reference
Ampacity values are for reference only. Actual current capacity depends on insulation temperature rating, ambient temperature, bundling, altitude, and local electrical codes. Ampacities below 23 AWG are omitted because voltage drop typically limits current before thermal ampacity does. Always consult the NEC (NFPA 70) or a licensed electrician for electrical installations.
WIRE GAUGE GUIDE
Understanding Wire Gauge — Why Higher Gauge = Thinner Wire
A higher gauge number means a thinner wire — counterintuitive but logical. The AWG system is logarithmic, not linear. Learn the rules that let you estimate any wire size in your head.
01
Origin of the Gauge System
Higher gauge = thinner wire. The gauge number counts how many times the wire was drawn through progressively smaller dies. A wire drawn through 30 dies (30 AWG) is thinner than one drawn through 10 dies (10 AWG). The system is logarithmic, not linear.
02
Key Scaling Rules
Every 3 AWG decrease: area doubles, resistance halves (12 AWG → 9 AWG).
Every 6 AWG decrease: diameter doubles (16 AWG → 10 AWG).
Every 10 AWG decrease: resistance and mass change by factor of ~10 (20 AWG → 10 AWG).
03
Aught Notation & Memory Anchor
For sizes larger than 1 AWG: 1/0 = one aught, 2/0 = two aught, etc. Above 4/0, system switches to MCM (thousands of circular mils) — roughly 2 MCM ≈ 1 mm².
Memory anchor: 10 AWG = 0.10″ (2.59 mm), 5.26 mm², ~1 Ω/1,000 ft.
AWG Scaling Rules at a Glance
Once you know 10 AWG (2.59 mm, 5.26 mm², 0.999 Ω/1,000 ft), everything else scales from there.
−3 AWG
Area ×2 · Resistance ×0.5
−6 AWG
Diameter ×2
−10 AWG
Resistance ×0.1 · Mass ×0.1
10 AWG
2.59 mm · 5.26 mm² · 1 Ω/1,000 ft
CROSS-REFERENCE
AWG & Sheet Metal — The B&S Connection
The B&S/AWG system governs both electrical wire and aluminum sheet metal thickness. The same gauge progression that sizes your wire also sizes your aluminum enclosure panels.
| Gauge | Wire Diameter (mm) | Wire Area (mm²) | Aluminum Sheet (mm) | Application |
|---|---|---|---|---|
| 10 | 2.588 | 5.26 | 2.588 | Power wire / RF enclosure |
| 12 | 2.053 | 3.31 | 2.053 | Branch circuits / chassis |
| 14 | 1.628 | 2.08 | 1.628 | Lighting / instrument panels |
| 16 | 1.291 | 1.31 | 1.290 | Appliance wire / automotive |
| 18 | 1.024 | 0.823 | 1.024 | Control wiring / light brackets |
| 20 | 0.812 | 0.518 | 0.813 | Signal wiring / electronic enclosures |
Note: Aluminum sheet uses the same B&S/AWG system as electrical wire. 16 AWG wire = 1.291 mm diameter; 16 gauge aluminum sheet = 1.290 mm thickness. The near‑identical values (within 0.001 mm) are not a coincidence — they share the same gauge standard.
Wire Gauge Ampacity — Why Different Charts Show Different Ratings
Ask any engineer who has compared wire gauge charts from different sources, and they will confirm: the ampacity numbers rarely match. Engineering Toolbox, PowerStream, the NEC, and manufacturer datasheets all give different current ratings for the same gauge. The reason: they assume different thermal conditions.
| Scenario | Heat Dissipation | Relative Ampacity | Typical Application |
|---|---|---|---|
| Chassis wiring — single wire in free air | Excellent | ~1.6–2.0× higher | Point‑to‑point wiring inside equipment, open‑air bus bars, test leads |
| Power transmission — bundled in conduit or cable | Poor | Base reference | Building wiring in conduit, multi‑conductor cables, wire harnesses |
| NEC residential — per NFPA 70 code tables | Regulated | Code‑defined (conservative) | Branch circuits in residential and commercial buildings |
A wire’s current capacity is limited by how much heat its insulation can withstand before degrading. How fast that heat dissipates depends entirely on the installation environment. The same wire can safely carry twice the current in free air as it can bundled inside a conduit. Chassis wiring (single wire in open air) has the highest rating; power transmission (multiple conductors bundled in conduit) has the lowest because heat has nowhere to escape.
Always consult the NEC (NFPA 70) or a licensed electrician for code‑compliant installations. The insulation temperature rating (75°C, 90°C, etc.) also affects ampacity — higher‑rated insulation allows more current. Ampacity values on this page are for reference only and assume typical 75°C rated insulation.
WIRE GAUGE CALCULATOR
Stranded Wire AWG — How to Calculate Equivalent Gauge
Stranded wire consists of multiple thin strands twisted together. Its AWG is specified by the equivalent cross‑sectional area of all strands combined, not by the diameter of the overall bundle. A 12 AWG stranded wire has the same total copper cross‑section as a 12 AWG solid wire (3.31 mm²), even though the bundle diameter is slightly larger due to air gaps.
Key concept: The equivalent AWG of stranded wire is based on the total copper area, not the outer diameter. Calculate it by measuring a single strand, computing its area, multiplying by the number of strands, then converting to AWG. The interactive calculator above does this automatically.
Step 1
Measure a Single Strand
Use a micrometer or calipers to measure the diameter of one individual strand in mm. Record this value as d. For stranded wire, strands are typically all the same diameter — measure one strand and multiply by the total count.
Step 2
Calculate Total Area
A₁ = (π/4) × d² — area of one strand.
A_total = A₁ × N — multiply by the number of strands.
Then convert to AWG using: AWG = 36 − 4.3124 × ln(A_total) − 4.3686, where A_total is in mm².
Common Configurations
Strand Counts & Applications
7‑strand (1 center + 6 around) — most common for 10–18 AWG.
19‑strand — more flexible, used for 6–10 AWG.
37‑strand — high‑flex applications. Conductors above 6 AWG are almost always stranded because solid wire is too stiff to route practically.
Example Calculation — 7‑Strand Wire
A wire has 7 strands, each 0.32 mm in diameter.
A₁ = (π/4) × (0.32)² = 0.0804 mm² per strand.
A_total = 0.0804 × 7 = 0.563 mm².
AWG = 36 − 4.3124 × ln(0.563) − 4.3686 ≈ 20 AWG.
The stranded wire calculator in the interactive section above does this automatically — input your strand count and diameter to get the equivalent AWG and total cross‑sectional area.
7‑Strand
1+6 configuration
19‑Strand
6–10 AWG standard
37‑Strand
High‑flex applications
WIRE GAUGE FAQ
Frequently Asked Questions
AWG (American Wire Gauge) is the North American standard for measuring solid, nonferrous electrical wire, standardized under ASTM B258. Range: 4/0 (11.684 mm) to 40 AWG (0.079 mm). Higher AWG = thinner wire — counterintuitive because the system counted wire drawing passes: more passes = thinner wire = higher gauge number. Every 6‑gauge decrease doubles the diameter.
AWG is the American standard; SWG (Standard Wire Gauge, BS 3737) is the British/Commonwealth standard. At the same gauge number, SWG is typically thicker. Example: 10 SWG = 3.25 mm vs. 10 AWG = 2.59 mm — a 25% difference. When ordering internationally, always specify the gauge standard and the diameter in millimeters to avoid errors. Full comparison details in the AWG vs. SWG section.
AWG measures diameter; mm² measures cross‑sectional area (per IEC 60228). Formula: AWG = 36 − 4.3124 × ln(area_mm²) − 4.3686. Key reference points: 10 AWG ≈ 5.26 mm², 12 AWG ≈ 3.31 mm², 14 AWG ≈ 2.08 mm². Use the interactive calculator at the top of this page for instant conversion.
Per NEC: 12 AWG copper for 20A branch circuits; 14 AWG for 15A circuits. For chassis wiring (free air), 18 AWG can handle up to 16A at 75°C — but verify thermal conditions.
Charts differ because they assume different conditions: chassis wiring (free air) shows up to 2× higher ampacity than power transmission (bundled in conduit). Insulation temperature rating (60°C vs. 90°C) further shifts numbers. Always check which scenario your chart assumes. See the Ampacity section for a detailed explanation.
Measure one strand diameter (d). Calculate: A₁ = (π/4) × d² (area per strand). Multiply by strand count: A_total = A₁ × N. Then convert: AWG = 36 − 4.3124 × ln(A_total) − 4.3686.
Example: 7 strands × 0.32 mm ≈ 20 AWG. Use the stranded wire calculator in the interactive section to do it automatically. See the Stranded Wire AWG section for a detailed walkthrough.
Wire EDM typically uses 0.1–0.3 mm wire — approx. AWG 38–29. Thinner (0.1 mm / 38 AWG) enables finer detail but cuts slower; thicker (0.3 mm / 29 AWG) cuts faster but limits minimum feature size. Baetro’s wire EDM services use the full range.
AWG vs. sheet metal: The B&S/AWG system also governs aluminum sheet thickness — same gauge numbers, same logarithmic progression. Carbon steel uses MSG (different system). Bookmark the sheet metal gauge chart for fabrication.
Download Free Printable Wire Gauge Chart PDF
This one-page reference covers AWG 4/0 through 40 with diameter, cross‑sectional area, resistance, weight, and ampacity for both chassis wiring and power transmission. The reverse side includes AWG ↔ SWG comparison, stranded wire calculation method, and common household wire sizes (15A → 14 AWG, 20A → 12 AWG, 30A → 10 AWG). Baetro‑branded with EDM and electronics manufacturing information — print it for your shop wall or toolbox.