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Wire Size Calculator
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This Wire Size Calculator recommends a copper wire gauge (AWG) for a given load current, using a standard reference ampacity table and the common 80% derating practice for continuous loads (electrical codes generally require conductors sized for at least 125% of a continuous load's current). Enter your load current in amps, and the calculator suggests the smallest wire gauge from the reference table that comfortably handles it. This is a simplified planning reference — always verify against your local electrical code, insulation type, and installation conditions before wiring anything. Everything runs locally in your browser. Scroll down to enter your load current.
Features
- Recommends a wire gauge (AWG) from load current
- Applies standard 80% continuous-load derating
- Reference ampacity table for common copper wire sizes
- Instant recalculation as you adjust the load
Why use this wire size calculator?
- Quick first-pass reference before consulting an electrician
- No need to memorize an ampacity table
- Fully private — nothing uploaded
- Free with unlimited use
Frequently asked questions
Why is there an 80% derating applied?
Many electrical codes require conductors for continuous loads (running 3+ hours) to be sized for at least 125% of the actual current, which is equivalent to only using 80% of a wire's rated ampacity — this calculator applies that same safety margin.
Is this a substitute for consulting an electrician or electrical code?
No, this is a simplified planning reference; actual wire sizing depends on insulation type, ambient temperature, conduit fill, run length (voltage drop), and your local electrical code — always verify with a licensed electrician.
What wire material does this assume?
Standard copper conductor ampacity ratings; aluminum wire has different (generally lower) ampacity ratings for the same gauge.
Does this account for voltage drop over long wire runs?
No, ampacity and voltage drop are separate concerns — use the site's Voltage Drop Calculator alongside this one to check long cable runs.
What AWG range does this cover?
This reference table covers common sizes from 14 AWG up to 4/0 AWG; loads beyond that range need a qualified electrician's sizing.