Voltage Drop Calculator

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Calculate cable voltage drop, load-end voltage, power loss, and maximum length for copper or aluminum conductors in DC, single-phase, and three-phase circuits.

Input Parameters

Circuit Type

Select the return path model.

Conductor Material

Material affects conductor resistance.

Conductor Size

Use one conductor size for the current path.

One-way Cable Length

Physical one-way distance from source to load.

Load Current

Continuous load current.

Source Voltage

Supply voltage at the source side.

Allowed Voltage Drop

Used to estimate maximum cable length.

Results

Voltage Drop

Voltage Drop Percent

Load-end Voltage

Cable Power Loss

Max Length by Allowed Drop

Design Note

Equations Used

DC / Single-phase: V_drop = I × R_{per m} × Length × 2

Three-phase: V_drop = √3 × I × R_{per m} × Length

Drop Percent: Drop % = V_drop / V_source × 100%

Power Loss: P_loss = V_drop × I

Max Length: L = V_{allowed drop} / cable drop coefficient

Frequently Asked Questions (FAQ)

Q1: Why does voltage drop increase with cable length?
Longer cable has more resistance, so the voltage loss increases in proportion to length and current.

Q2: Why does DC use a factor of 2?
A two-wire DC or single-phase circuit has both supply and return conductors, so the current travels through twice the one-way length.

Q3: Why is three-phase voltage drop different?
Balanced three-phase line-to-line voltage drop uses the √3 factor rather than a simple two-wire round trip model.

Q4: Can I use this calculator for USB cables?
Use the dedicated USB cable voltage drop calculator for USB-specific current and conductor assumptions. This tool is general-purpose.

Q5: What voltage drop is acceptable?
It depends on the application. Low-voltage electronics often need tighter limits than lighting or power distribution.

Q6: Does temperature affect voltage drop?
Yes. Copper and aluminum resistance increase with temperature, so real voltage drop can be higher in hot environments.

Disclaimer: This calculator provides electrical resistance-based estimates. Actual voltage drop can vary with conductor temperature, cable construction, installation method, connectors, harmonics, and local wiring standards.

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