Voltage Drop Distance Limit

Maximum Wire Distance Calculator for Fixed Voltage Drop

Planning outdoor lighting, driveway gates, shed feeds, and detached garage circuits. Determines the maximum allowable one-way run length in feet or meters before voltage drop exceeds target threshold (e.g. 3% branch / 5% total).

Maximum Wire Distance Calculator for Fixed Voltage Drop
AWG Copper
Amps
Volts
% Drop
Calculated Result
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Instant Calculation
Engineering Output
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Auxiliary Output
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Step-by-Step Derivation ▼ Show Steps
Governing Formula Verified Physics
L_max = (ΔV_max × A_cmil) / (2 × K × I)  (1-Phase)  |  K_Cu ≈ 12.9

Calculations adhere to standard electrical engineering physics and National Electrical Code (NFPA 70) regulations.

Engineering Principles & Calculations

This calculator uses the exact mathematical relationships between Wire Gauge (AWG), Circuit Amps (A), Circuit Voltage (V), Allowed Drop (%), Material (Copper/Aluminum) to determine Maximum Safe Run Distance (Feet & Meters). In practical installations, factors such as ambient raceway temperature, harmonic distortion, duty cycle continuous operation, and conductor impedance must be accounted for by a certified electrician.

Determines the maximum allowable one-way run length in feet or meters before voltage drop exceeds target threshold (e.g. 3% branch / 5% total).

Typical Application & Industry Guidelines

Planning outdoor lighting, driveway gates, shed feeds, and detached garage circuits.

Reference Matrix

Maximum Wire Distance Calculator for Fixed Voltage Drop Benchmark Lookup Table

Wire Gauge120V @ 12A (15A Ckt)120V @ 16A (20A Ckt)240V @ 24A (30A Ckt)
14 AWG Copper48 Feet36 Feet72 Feet
12 AWG Copper76 Feet57 Feet114 Feet
10 AWG Copper121 Feet90 Feet181 Feet
8 AWG Copper192 Feet144 Feet288 Feet
6 AWG Copper305 Feet229 Feet458 Feet
4 AWG Copper485 Feet364 Feet728 Feet
FAQ

Frequently Asked Questions

How far can I run a 12 AWG wire on a 20A circuit? +
At an 80% continuous load (16 Amps) on a 120V circuit, 12 AWG copper wire reaches its 3% voltage drop limit at approximately 57 feet. Beyond 57 feet, step up to 10 AWG wire.
What is the NEC recommendation for voltage drop? +
NEC Informational Note 210.19(A) recommends limiting branch circuit voltage drop to 3%, and total feeder plus branch circuit drop to 5%.
Why does 240V double the allowable wire distance? +
Because the allowable 3% drop at 240V is 7.2V compared to 3.6V at 120V, you can run wire twice as far for the same percentage loss.

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