Industrial Cable Length / Voltage Drop Design Calculator
Compare practical cable size candidates by voltage drop, load voltage, and design threshold for industrial runs.
Design Inputs
Design Recommendation
| Size | Drop (V) | Drop (%) | Load V | Status |
|---|
⚠️ Engineering Caution:
This tool is intended for screening and pre-check workflows. Results are usually directionally useful, but they
can still shift with equipment selection, environmental conditions, naming conventions, revision status, or
interpretation rules. Confirm any value that affects ordering, substitution, compliance, or installation before
acting on it.
Frequently Asked Questions
How is this different from a normal voltage drop calculator?
This tool compares multiple cable size candidates and highlights a practical first passing option under your chosen drop criterion. It is meant for design screening rather than a single fixed-size check.
Can I compare copper and aluminum runs?
Yes. The calculator supports practical resistance assumptions for copper and aluminum candidate sizes so you can compare design outcomes quickly.
What This Calculator Is For
A basic voltage drop calculator answers a simple question: what is the drop for this one conductor size? In real industrial design work, that is usually only the first step. Engineers and technicians often need a more practical selection workflow:
- What cable sizes are likely to meet a target drop limit?
- How does copper compare to aluminum for this run?
- Which candidate size is the first practical option under a chosen design threshold?
- How much load voltage remains at the equipment for each size?
This tool is designed as a cable selection and design helper rather than a single-result voltage-drop calculator.
What It Calculates
Given system type, source voltage, load current, conductor material, one-way length, and a target voltage-drop limit, the tool compares several practical cable size candidates and reports:
- estimated voltage drop in volts
- drop percentage
- voltage at load
- whether the size passes the target design threshold
- a recommended first passing size
Core Relationships
The same practical resistance-based approach is used as a standard voltage drop estimate:
- Single-phase:
Vdrop = 2 × L × I × R - Three-phase:
Vdrop = √3 × L × I × R
Where R is conductor resistance per unit length and L is one-way distance.
The key difference is that this tool evaluates multiple conductor sizes and presents them as design candidates instead of only returning one result.
Practical Use Cases
This tool is useful for:
- preliminary equipment feeder design
- industrial cable run planning
- comparing copper versus aluminum options
- checking whether a longer run needs a larger conductor size
- creating a fast design shortlist before detailed code review
Important Limitations
This tool is a practical planning helper. Final cable selection still depends on more than voltage drop alone, including:
- ampacity and insulation temperature rating
- conduit fill and bundling
- ambient temperature and derating
- fault current and protection coordination
- local code and project standards
Use this calculator to narrow candidates quickly, then confirm final selection against applicable code and project rules.
FAQ
How is this different from a normal voltage drop calculator?
A normal voltage drop calculator usually checks one selected conductor size. This tool compares multiple candidate sizes and helps you choose a practical starting point for design.
Can I use this for three-phase motor feeders?
Yes. It is useful for quick three-phase feeder planning, especially when comparing candidate sizes against a target drop percentage.
Does this replace ampacity checks?
No. Voltage drop is only one part of cable selection. Ampacity, derating, and protection still must be checked separately.