Multi-segment cable voltage drop calculator

Total up voltage drop across a multi-segment cable run — useful for harnesses and daisy-chained power — from each segment's length and conductor area.

Load current

Drawn by the load at the far end

System voltage

DC, or AC line voltage

Circuit type

Conductor material

Single-phase: drop = 2 × ρ × L × I ÷ A per segment

Cable segments

Add each piece of the run. Connectors and terminals add their own small drop — include them as short segments.

Segment 1

Length

Cross-section

Segment 2 (optional)

Length

Cross-section

Segment 3 (optional)

Length

Cross-section

Segment 4 (optional)

Length

Cross-section

Results

Segment 1 drop: 6.9V
Total voltage drop: 6.9V
Share of system voltage: 28.73%

Exceeds the 5% feeder guideline — increase the conductor cross-section or shorten the run.

This assumes the full load current flows through every segment. In a true daisy chain, current only accumulates up to each tap point.

Browse related parts:

cable wire harness terminal blocks

Frequently asked questions

How do I add up voltage drop across multiple cable segments?

Each segment contributes a drop of k × ρ × L × I ÷ A, where ρ is 0.01724 Ω·mm²/m for copper or 0.0282 for aluminium, k is 2 for single-phase or √3 for three-phase, L is the segment length and A the conductor area. The tool sums the segment drops and shows the total as a share of system voltage.

What is an acceptable voltage drop for a harness or daisy-chain feed?

The calculator compares the total against the usual 3% branch-circuit and 5% feeder guidelines. A total over 5% flags a warning to increase cross-section or shorten the run; between 3% and 5% it notes you are inside the feeder allowance but should verify the application.

Does the calculator assume full current flows through every segment?

Yes — the model passes the full load current through each segment, which gives a conservative upper bound. In a true daisy chain the current only accumulates up to each tap point, so a real feed usually drops less than the estimate. Connector and terminal contact drops can be entered as short segments.

How it works

Every segment contributes its own drop: resistance is R = ρ × L ÷ A, multiplied by the current and the two-way (single-phase) or √3 (three-phase) factor. The tool sums the segment drops and expresses the total as a share of the system voltage. IC Source Direct compares that against the usual 3% branch-circuit and 5% feeder guidelines.

Every connector or terminal in the run adds its own small contact drop — enter them as short segments. In a daisy-chained feed, each load only draws current up to its tap point, so the model gives a conservative upper bound.

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