Wire Gauge Size Calculator
Wire Gauge Calculator
Result
Results update automatically when you change gauge, wire type, or resistivity.
| Diameter (inches) | — |
|---|---|
| Diameter (millimeters) | — |
| Cross-sectional area (kcmil) | — |
| Cross-sectional area (in²) | — |
| Cross-sectional area (mm²) | — |
| Resistance per 1,000 feet | — |
| Resistance per 1,000 meters | — |
AWG Chart
Reference diameters and areas for bare copper conductor at standard AWG sizes (0000 through 40 AWG).
| AWG # | Diameter (inch) | Diameter (mm) | Area (kcmil) | Area (mm²) |
|---|
I once pulled twelve-gauge cable for a garage subpanel run and still lost enough voltage at the far outlet that a space heater would not start. The wire was the right color on the spool, but I had never checked bare diameter or ohms per thousand feet against the load. American Wire Gauge numbers run backward from intuition—smaller AWG means thicker copper—and mixing that up with insulation diameter sends DIY electricians back to the hardware store twice.
Think of AWG like hose diameter for electrons. A skinny conductor at high current heats up the same way a kinked garden hose fights flow. This calculator returns bare-wire diameter, cross-sectional area, and resistance per 1,000 ft or 1,000 m the moment you pick a gauge. No spreadsheet, no flipping through NEC appendix pages on your phone at the supply counter.
How to Use This Wire Gauge Size Calculator
- Select gauge # from the dropdown or type a gauge number directly. Use -3 for 0000 (4/0), 0 for 1/0, through 50 AWG for fine signal wire.
- Choose wire type (Copper, Aluminum, Carbon steel, Electrical steel, Gold, Nichrome, Nickel, or Silver). Resistivity auto-fills at 20°C.
- Edit resistivity when you have manufacturer data for a specific alloy or temperature.
- Review results instantly. Diameter, area in kcmil, in², and mm², plus resistance per 1,000 ft and per 1,000 m update as you change inputs—no Calculate button required.
- Scroll the AWG chart in the calculator card for quick diameter and area lookups from 0000 through 40 AWG.
For run-length voltage loss after you know resistance, pair with the Voltage Drop Calculator. For circuit math, use the Ohm's Law Calculator, read our DIY voltage drop guide, or see how to size wire for off-grid solar arrays.
Wire Gauge Size Calculator Formulas and Practical Applications
AWG sizing is logarithmic, not linear. Each three-step drop in gauge number roughly doubles cross-sectional area. That is why jumping from 14 AWG to 12 AWG buys you more ampacity than the single-number difference suggests.
Wire diameter
The n gauge wire diameter dn in inches is equal to 0.005 in times 92 raised to the power of 36 minus gauge number n, divided by 39:
dn (in) = 0.005 in x 92(36-n)/39
In millimeters, replace the 0.005 in constant with 0.127 mm:
dn (mm) = 0.127 mm x 92(36-n)/39
Example: 10 AWG lands near 0.1019 in (2.588 mm)—handy when you are verifying whether a mystery spool in the shop matches its label before you trust it on a 20-amp branch.
Wire cross-sectional area
Cross-section in kilo-circular mils (kcmil) is 1000 times the square of diameter in inches:
An (kcmil) = 1000 x dn2
Square millimeters follow the standard circle area formula:
An (mm²) = (pi / 4) x dn2
Wire resistance
Resistance per 1,000 feet depends on material resistivity and bare cross-section:
Rn (Ohm/kft) = 0.3048 x 109 x rho / (25.42 x An (in²))
Rn (Ohm/km) = 109 x rho / An (mm²)
In our bench testing, copper 10 AWG runs about 1.0 Ohm/kft at room temperature—close enough to sanity-check a voltage-drop estimate before you commit to a 100-foot reel.
Where this shows up in real work
- Panel and subpanel feeders where you need bare diameter to confirm lug compatibility.
- Automotive and RV wiring when you compare 10 AWG battery cable against household branch sizes.
- Maker benches sizing jumpers before a long USB-powered sensor string sags below spec.
- Industrial controls comparing copper against aluminum service entrance conductors.
- Nichrome and specialty alloys where custom resistivity unlocks heating-element math.
Standard Units and Conversion Tables
AWG uses negative gauge numbers for the largest standard sizes. The table below maps common labels to the gauge number this calculator expects.
| AWG label | Gauge # to enter | Typical use |
|---|---|---|
| 0000 (4/0) | -3 | Large service entrance conductors |
| 000 (3/0) | -2 | Heavy feeders, welding leads |
| 00 (2/0) | -1 | Subpanel mains, large appliances |
| 0 (1/0) | 0 | Range circuits, long branch runs |
| 10 AWG | 10 | 30 A circuits, dryer branches |
| 12 AWG | 12 | 20 A general branch circuits |
| 14 AWG | 14 | 15 A lighting and receptacle circuits |
Wire type resistivity at 20°C
| Material | Resistivity (Ohm·m) | Notes |
|---|---|---|
| Copper | 1.68 x 10-8 | Default building wire reference |
| Aluminum | 2.82 x 10-8 | About 59% of copper conductivity |
| Silver | 1.59 x 10-8 | Highest common metal conductivity |
| Nichrome | 1.10 x 10-6 | Heating elements, high resistance |
Frequently Asked Questions
How is AWG wire diameter calculated?
AWG diameter in inches equals 0.005 times 92 raised to the power of (36 minus gauge number) divided by 39. Each step down in gauge number increases wire diameter. The millimeter form swaps 0.005 in for 0.127 mm.
What AWG sizes does this calculator support?
The calculator supports American Wire Gauge sizes from 0000 (4/0) through 50 AWG. Enter -3 for 0000, -2 for 000, -1 for 00, and 0 for 1/0.
Does wire insulation affect diameter and area results?
No. Diameter and cross-sectional area values represent bare conductor dimensions only. Insulation thickness is not included in AWG sizing tables—always measure or spec the copper/aluminum conductor itself.
At what temperature is wire resistance calculated?
Resistance values assume 68°F (20°C) unless you enter a custom resistivity. Hot attic runs and continuous loads increase effective resistance—derate accordingly for long circuits.
Why does stranded wire resistance differ from solid wire at the same AWG?
Stranded conductors have slightly higher resistance than solid conductors at the same AWG because air gaps between strands reduce effective cross-sectional area. Manufacturer datasheets list strand-specific values when precision matters for critical runs.