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Wire Size Calculator

Find a practical wire size based on current, voltage, distance, material, and installation assumptions for electrical planning and study.

Use calculator Open circuit simulator
Professional workflow

Estimate conductor sizing faster while keeping voltage drop and ampacity in view.

Wire size is constrained by ampacity, voltage drop, conductor material, and installation conditions.
  • Designed for early conductor selection before checking official ampacity and derating tables.
  • Combines current demand and run length so users do not size wire from amps alone.
  • Helps compare copper vs. aluminum choices without hiding the safety limitations.

Calculate recommended wire size based on current

💡 Validates both voltage drop and ampacity for safety

Start with 3% for branch-circuit planning, then adjust for your design standard.
The final conductor must satisfy ampacity, derating, voltage drop, and local code requirements.
For long runs, voltage drop may require a larger wire than ampacity alone suggests.

Standard sizes: 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240 mm²

Ampacity based on IEC 60364-5-52 (Method C)

Inputs to prepare
  • Load current or calculated amps
  • Circuit voltage
  • One-way distance
  • Conductor material
  • Voltage-drop target and installation assumptions
Worked example

Example: 30 A load at 240 V

Given
  • • 30 A load
  • • 240 V circuit
  • • 100 ft one-way run
  • • Copper conductor
Steps
  1. 1. Enter the load current, voltage, run length, and material.
  2. 2. Review both voltage drop and the candidate conductor size before checking code tables.
A longer 30 A run may require upsizing beyond the minimum ampacity conductor to keep voltage drop under a 3% planning target.
Common use cases
  • Branch circuit planning
  • Feeder pre-sizing
  • Study comparisons between AWG sizes and voltage drop
How to read results
  • Treat the suggested size as a planning candidate, then verify ampacity and derating.
  • Longer distances may require a larger conductor even when current is unchanged.
  • If voltage drop is acceptable but ampacity is not, ampacity controls the final size.
Code and safety notes
  • Conductor ampacity depends on insulation rating, ambient temperature, bundling, and terminals.
  • Equipment grounding conductors, neutral sizing, and continuous-load rules may require separate checks.
  • Always verify against the code edition and tables used in your jurisdiction.

Frequently asked questions

What affects wire size?

Current, conductor material, run length, voltage drop limits, insulation, installation method, and code rules all matter.

Can this replace code tables?

No. It speeds up planning, but code tables and professional verification are required for real work.

Does longer wire need larger size?

Often yes. Longer runs increase resistance and voltage drop, which may require a larger conductor.

Is it useful for DIY projects?

It can help you understand the tradeoffs, but electrical work should follow local rules and safety requirements.