Wire Gauge Calculator

Calculate wire gauge with voltage drop, ampacity, temperature correction, and multiple conductor materials.

Basic Calculation
Advanced Calculation
AWG Converter

Voltage Drop Formula: Vdrop = K × L × I × R / 1000 × cosθ

Where: K = 2 (Single Phase) or √3 (Three Phase), L = Length (ft), I = Current (A), R = Resistance (Ω/kft), cosθ = Power Factor

Maximum current the wire will carry
System voltage
Electrical system phase configuration
One-way distance from source to load
Copper: 100% conductivity
Aluminum: 61% conductivity
CCA: 70% conductivity
Steel: 10% conductivity
Silver: 106% conductivity
Maximum allowable voltage drop percentage
Power factor for reactive loads (1.0 for resistive loads)
Advanced Parameters

For more precise calculations including temperature, installation method, and environmental factors.

Wire insulation temperature rating
How the wire will be installed
Expected ambient temperature
Percentage of conduit filled with wires
Number of conductors in conduit or bundle

AWG Converter: Convert between AWG, mm², and inches. American Wire Gauge (AWG) is a standardized wire gauge system.

AWG to Metric
Metric to AWG
American Wire Gauge size
mm²
circular mils
Enter cross-sectional area in mm² or circular mils
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Understanding Wire Gauge

Wire gauge refers to the physical size of the wire, which determines how much current it can safely carry. The American Wire Gauge (AWG) system is the standard for measuring wire diameter in North America.

Key Wire Properties:

  • Ampacity: Maximum current a wire can carry without exceeding its temperature rating
  • Voltage Drop: Reduction in voltage between source and load due to wire resistance
  • Resistance: Opposition to current flow, measured in ohms per unit length
  • Cross-Sectional Area: Physical area of the wire's conductor

Material Properties

Copper

Conductivity: 100% (Reference)

Temp Coefficient: 0.00393/°C

Applications: Most electrical wiring, high reliability

Aluminum

Conductivity: 61% of copper

Temp Coefficient: 0.00403/°C

Applications: Power transmission, lightweight

Copper-Clad Aluminum

Conductivity: 70% of copper

Temp Coefficient: 0.00400/°C

Applications: Cost-effective wiring

Steel

Conductivity: 10% of copper

Temp Coefficient: 0.00500/°C

Applications: Structural strength, grounding

Silver

Conductivity: 106% of copper

Temp Coefficient: 0.00380/°C

Applications: High-frequency, premium audio

Temperature Correction

Wire resistance increases with temperature according to the formula:

RT = R20 × [1 + α × (T - 20)]

Where:

  • RT = Resistance at temperature T
  • R20 = Resistance at 20°C
  • α = Temperature coefficient of resistance
  • T = Ambient temperature in °C

American Wire Gauge (AWG) Standard

AWG Size Diameter (mm) Area (mm²) Copper Ampacity* Aluminum Ampacity* Resistance (Ω/kft)

*Ampacity ratings based on 75°C insulation, copper conductor, in free air at 30°C. Actual ratings vary with conditions.

Factors Affecting Wire Selection

1

Current Load: The amount of current the wire must carry determines minimum gauge

2

Wire Length: Longer wires have higher resistance, requiring larger gauge to limit voltage drop

3

Voltage Drop Tolerance: Acceptable percentage of voltage loss from source to load

4

Conductor Material: Different materials have different conductivity and temperature coefficients

5

Temperature Rating: Higher temperature insulation allows for higher ampacity ratings

6

Installation Method: Free air, conduit, or bundled installation affects heat dissipation

Common Applications

  • Residential Wiring: 14 AWG for lighting, 12 AWG for outlets, 10 AWG for appliances
  • Automotive: 16-10 AWG for various circuits depending on current draw
  • Industrial: 8 AWG and larger for high-power equipment
  • Low Voltage: 18-24 AWG for control circuits, electronics, and telecommunications
  • Service Entrance: 4/0 to 2/0 AWG for main service panels

Safety Note: Always follow local electrical codes and regulations when selecting and installing wiring. Undersized wires can overheat and create fire hazards. When in doubt, consult with a licensed electrician.

Frequently Asked Questions

Temperature affects wire resistance: higher temperatures increase resistance, which increases voltage drop and reduces ampacity. For every 10°C increase above the rated temperature, ampacity decreases by approximately 10-15%. Additionally, wire resistance increases with temperature according to the formula RT = R20 × [1 + α × (T - 20)].

Installation method affects heat dissipation: Wires in free air dissipate heat better than wires in conduit. Bundled wires or wires in crowded conduits have reduced ampacity because they can't dissipate heat as effectively. Typical derating factors: Free air = 1.0, Conduit = 0.8, Bundled = 0.7, Direct burial = 0.9, Underground conduit = 0.7.

Copper has 61% better conductivity than aluminum, so a copper wire can carry more current than an aluminum wire of the same size. However, aluminum is lighter and less expensive. For equivalent current carrying capacity, you need aluminum wire about 2 AWG sizes larger than copper. Aluminum also requires special connectors to prevent oxidation and ensure proper connections.

Excessive voltage drop can cause: 1) Equipment malfunction or failure to operate, 2) Reduced efficiency and increased energy costs, 3) Overheating of motors due to reduced voltage, 4) Premature failure of electrical components. For most applications, voltage drop should not exceed 3% for branch circuits or 5% for the entire circuit (feeder + branch).

For future expansion, consider: 1) Size wires for 125-150% of current load, 2) Use larger conduit to allow for additional wires, 3) Consider higher temperature rated insulation, 4) Install subpanels to reduce long wire runs, 5) Document all wiring for future reference. A good rule is to size wires one gauge larger than currently needed.