This calculator helps you find the diameter of a wire based on the American Wire Gauge (AWG) standard.
Explore various tools related to wire gauge conversions and measurements:
Our Wire Gauge Calculator helps electricians, engineers, and DIY enthusiasts select the correct American Wire Gauge (AWG) size for any electrical application. By accounting for current load, voltage drop, conductor length, and insulation type, you can ensure optimal performance, energy efficiency, and safety compliance. Read on for detailed explanations, step-by-step instructions, practical examples, and best practices.
Wire gauge refers to a standardized system of measuring the diameter of electrical conductors. In the United States, the AWG scale is used, where smaller gauge numbers indicate larger diameters (e.g., 4 AWG is thicker than 12 AWG). Choosing the right gauge prevents overheating, minimizes voltage drop, and ensures that wiring meets code requirements.
While AWG is common in North America, many countries use metric sizing in square millimeters (mm²). Our calculator can convert between AWG and mm² to support international projects.
For reference, here are a few common sizes:
Undersized conductors can overheat under load, trip breakers, or cause fire hazards. Oversized conductors add unnecessary cost and bulk. Accurate sizing balances safety, cost, and ease of installation.
National Electrical Code (NEC) and IEC standards specify ampacity tables for various insulation types and temperature ratings. Always consult local codes before finalizing conductor size.
Voltage drop (Vdrop) along a conductor is:
Vdrop = I × R × 2 × L
Where:
Resistance depends on conductor material (copper or aluminum) and gauge. For copper 12 AWG:
R ≈ 1.588 Ω per 1 000 ft ⇒ 0.001588 Ω/ft
Multiply by length and current to find voltage drop.
For a 50 ft run to a 15 A load using 12 AWG copper:
Vdrop = 15 × 0.001588 × 2 × 50 = 2.382 V
Percentage drop at 120 V = (2.382/120)×100 ≈ 1.99%
Aluminum has ~61% the conductivity of copper. For same ampacity you must increase gauge (e.g., 12 AWG Cu ≈ 10 AWG Al). Our calculator accounts for material selection automatically.
Enter your project parameters:
Click “Calculate” to display recommended AWG or mm² size, expected voltage drop, and ampacity compliance.
Upload CSV files with multiple circuits or integrate via our REST API to programmatically size conductors in electrical design software.
POST /api/wire-gauge
{
"current": 20,
"voltage": 240,
"length": 75,
"dropPercent": 3,
"material": "copper",
"insulationTemp": 90,
"units": "ft"
}
{
"recommendedGauge": "10 AWG",
"voltageDrop": 5.28,
"dropPercent": 2.20,
"ampacityOK": true,
"maxCurrent": 30
}
CSV must include headers: current, voltage, length, dropPercent, material, insulationTemp, units. Output file returns same columns plus recommendedGauge, voltageDrop, dropPercent, ampacityOK.
Plugins available for AutoCAD, Revit, and electrical estimation software to size conductors within your project drawings.
Standard home lighting and receptacle circuits often use 14 AWG (15 A) or 12 AWG (20 A). Ensure voltage drop under worst-case load does not exceed 3%.
Garage, outbuilding, or landscape lighting may require 100+ ft runs. Upsize gauge (e.g., from 14 AWG to 10 AWG) to control voltage drop and prevent dimming.
EV chargers draw high current (30–50 A). Use 6 AWG or larger copper conductors per NEC tables, adjust for length and continuous load requirements.
Three-phase feeders use larger conductors (4 AWG and up). Calculator supports multi-phase voltage drops and neutral sizing.
Motors have inrush currents. Use NEC adjustment factors and consider voltage drop at starting current to prevent nuisance trips.
DC circuits in solar installations use percent voltage drop limits of 1.5% for module-to-inverter runs. Our calculator includes DC mode with adjusted formulas.
Low-voltage signal cables may require voltage drop analysis for sensors. Calculator handles low-amp cases with high precision.
NEC and local amendments may impose stricter ampacity or derating rules. Use AHJ guidance for compliance.
Derate ampacity when multiple conductors share a raceway, or in high ambient temperatures. Our calculator prompts for conductor count and temperature to apply NEC correction.
Mark conductors with gauge and insulation type. Keep sizing calculations with project documentation for inspections and maintenance.
Ensure tight connections at terminations. Loose lugs increase resistance and heat, negating proper conductor sizing.
While larger wire reduces voltage drop, it adds weight, cost, and rigidity. Upsize only as needed for performance and safety.
A: Yes, but choose a larger AWG (typically two sizes up) to match copper ampacity. Aluminum requires anti-oxidation connectors and proper torque.
A: Underground conduit increases ambient temperature. Use conduit fill correction factors and select THHN/THWN-2 rated conductors for wet locations.
A: Size conductors individually for phase and neutral per NEC. Unbalanced neutral in 120/240 V circuits sees only differential current.
A: Negligible at power frequencies. Skin effect becomes significant in high-frequency applications (>1 kHz).
A: For runs under 50 ft at moderate currents (<10 A), voltage drop is often minimal. Our calculator shows percentage to confirm.
Selecting the correct wire gauge is critical for electrical safety, performance, and code compliance. Our Wire Gauge Calculator simplifies complex calculations, supports multiple conductor types and configurations, and integrates seamlessly with design and project workflows. Try it now to size conductors accurately, minimize voltage drop, and document your installation for inspections and future maintenance.
Real-world installations rarely match ideal conditions. Our calculator lets you apply derating factors for:
To adjust for ambient temperatures above 30 °C:
Conductor count in a raceway impacts heating:
Our calculator requests the number of parallel conductors and automatically applies the correct factor.
NEC allows branch-circuit conductors to be sized to unadjusted ampacity if only one circuit occupies the raceway, clarifying mixed-use installations.
For large currents, multiple conductors may be paralleled. Ensure each conductor meets the minimum gauge per NEC 310.10(H) and size equally to balance current sharing.
Nonlinear loads (VFDs, UPS, computers) produce triplen harmonics, causing neutral conductor overheating. Our calculator can incorporate:
When more than 150% of phase current flows in the neutral, size the neutral equal to phase conductors or larger, preventing hot neutrals in 4-wire systems.
Apply multipliers (e.g., 1.25× for 5–10% THD, 1.4× for 10–20% THD) to phase conductor ampacity to mitigate overheating.
A 30 A VFD drive with 15% THD needs conductor ampacity of 30 A × 1.25 = 37.5 A → size to 10 AWG (40 A rating) instead of 12 AWG.
In heavy industrial settings, cable trays may carry dozens of feeders. Group derating is essential; our tool models trays with up to 100 cables and calculates thermal resistances.
Beyond initial copper vs. aluminum cost, consider:
Calculate annual energy loss:
Loss (kWh) = I² × R × 2L × Hours per year ÷ 1000
Compare loss differences between gauge options to balance capital vs. operational expenses.
Copper: higher conductivity, smaller size, more expensive. Aluminum: lower cost, larger size, lighter weight. Our dual-material mode displays side-by-side cost/loss projections.
In corrosive or high-moisture settings, tinned copper or isolation barriers may be necessary. The calculator flags environments requiring specialized jackets (XHHW-2, MV-90).
Recyclability and lifecycle carbon footprint: copper has higher embodied energy; aluminum’s lower density reduces transport emissions. Our sustainability module estimates CO₂ impact per kilometer of cable run.
10 panels at 350 W each, 600 V DC array, 100 ft from inverter. DC voltage drop limited to 1.5%. Calculator recommends 6 AWG THHN copper, resulting in 0.9% drop.
1000 A three-phase feed, 50 ft run. Aluminum parallel conductors in enclosed busway required: choose 600 kcmil aluminum with 0.5% voltage drop and 40 °C ambient correction.
Level 2 charger, 48 A continuous load, 30 ft run. Use 4 AWG copper with 90 °C rating to meet NEC continuous load requirements and maintain <2% drop.
25 HP motor at 480 V, 20 A nominal, inrush ×6. Use 8 AWG copper, derated 125% for motor circuit, plus 1.4× for harmonics → size to 6 AWG.
200 ft run at 30 A, direct burial. PVC conduit in 25 °C soil. Calculator sizes 4 AWG copper XHHW-2 for <3% AC drop and includes soil thermal resistivity factor.
Service mast feeding four apartments at 100 A each. Use 4/0 AWG copper service entrance cable sized per NEC 310.15(B)(7) and grouping rules for meter-main arrangements.
Save common project settings as presets: “Residential Lighting,” “Commercial HVAC,” “Solar DC,” “Data Center,” and load them with one click. Share presets across project teams for standardized sizing.
Export preset libraries in JSON to share with colleagues. Integrate presets into your company’s electrical design toolkit for consistent application.
Track changes to presets—who modified ampacity factors or added new materials—using built-in version history. Roll back to previous configurations as needed.
Presets map directly into Revit parameter sets, enabling automated conductor schedules and material takeoffs based on calculator outputs.
Generate detailed reports showing all calculation steps, code references (NEC table citations), and safety margins. Use PDF or DOCX exports for permit submissions and inspection records.
Each report includes:
Certify reports with embedded digital signatures and timestamps to satisfy engineering stamp requirements and maintain legal integrity.
Enable “Inspector Mode” to highlight any non-compliant condition (e.g., percentage drop > 3%, unprotected conductors) in red for quick review.
When NEC or IEC standards update, calculator rules and code citations auto-refresh. Users receive notifications and can review change logs before applying to projects.
Access interactive tutorials, webinars, and one-on-one sessions. Our support team guides new users through complex derating and harmonics scenarios to ensure accurate application.
Our Wire Gauge Calculator extends far beyond simple ampacity tables. By incorporating derating factors, harmonics analysis, cost modeling, real-world case studies, and regulatory compliance tools, you gain a comprehensive solution for every electrical project. Start sizing conductors with confidence—optimize safety, efficiency, and cost-effectiveness from design through installation and maintenance.