Electrical Wire Calculator
Calculate the correct wire size for electrical circuits based on current, voltage, distance, and allowable voltage drop. Select wire gauge for safety and efficiency.
Step 1: Electrical Parameters
Voltage Drop Formula
Voltage Drop = (2 × Length × Current × Resistance) ÷ 1000
Based on NEC guidelines for safe electrical installations.
Step 2: Wire Specifications
Common Wire Sizes
Lighting: 14 AWG (15A)
Outlets: 12 AWG (20A)
Appliances: 10 AWG (30A)
Heavy Equipment: 8 AWG (40A)
Main Feed: 6 AWG (55A)
Wire Size Results
Recommended Wire Size
Wire Gauge Comparison
| Wire Gauge | Max Current | Diameter (mm) | Resistance (Ω/1000ft) |
|---|
Wire Size Calculation Formula
Voltage Drop = (2 × L × I × R) ÷ 1000
Where:
• L = One-way length of wire in feet
• I = Current in amperes
• R = Resistance of wire per 1000 feet (Ω/kft)
• 2 = Factor for round trip (source to load and back)
Wire Size Selection:
• Based on NEC Table 310.16
• Must satisfy both ampacity and voltage drop requirements
Example Calculation
Example: 20A circuit, 50ft, 120V, 3% max drop
Current: 20 Amps
Voltage: 120V
Distance: 50 feet
Max Drop: 3% (3.6V)
Calculation:
Allowable resistance = (Voltage Drop × 1000) ÷ (2 × L × I)
= (3.6 × 1000) ÷ (2 × 50 × 20) = 1.8 Ω/kft
From NEC table: 12 AWG has 1.93 Ω/kft (acceptable)
14 AWG has 3.07 Ω/kft (too high)
Result: Use 12 AWG wire
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