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Electrical Calculators

Voltage Drop

Estimate conductor voltage drop for copper or aluminum circuits.

01

Inputs

Conductor material

Circuit type

Load current

A

One-way circuit length

ft

Verified conductor resistance

Ω / 1,000 ft

Enter a resistance appropriate to the conductor size, material, and expected operating temperature.Nominal system voltage

V

02

Result & worksheet

7.26 V (3.03%)

Recorded summary

Material: Copper
Circuit: Single-phase / DC
Current: 20 A
One-way length: 150 ft
Estimated drop: 7.26 V / 3.03%

Formula used

VD = I × R × one-way length ÷ 1,000 × circuit multiplier

Calculation steps

20 A × 1.21 Ω/1,000 ft × 150 ft ÷ 1,000 × 2
Estimated load voltage: 232.74 V

Assumptions

Balanced steady-state load
Resistance is entered for the expected conductor operating temperature
Length is one-way; the circuit multiplier accounts for the return path

Verify before use

Verify conductor ampacity independently
Check equipment minimum-voltage requirements
Confirm conductor resistance source and temperature basis
Evaluate starting or inrush conditions where applicable