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Wire Gauge and Ampacity Selection

Compare copper and aluminum chart sizes using required ampacity, correction factors, terminal ratings and protection limits; save the full basis.

Use this result well

Inputs that matter
Cable and installation basis, Conductor material, Insulation column (°C), Limiting terminal column (°C), and 4 more
Output to expect
Conductor chart selection
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Conductor chart selection

Screen the published common sizes for copper or aluminum using a documented required load ampacity, overcurrent rating, insulation temperature, terminal limit and combined correction factor. This conservative comparison does not apply next-size-up, motor, parallel-conductor or dwelling-service exceptions. Aluminum sizes start at 8 AWG; missing chart cells are not filled in.

Allowed ampacity = min(insulation-column amperes × correction factor, terminal-column amperes); require load and breaker limits to fit.

Updated: September 2026

Example Scenarios

Try the built-in example, then replace its source data with your actual documented values. Retain failed comparisons and unresolved decisions.

→ 3/0 AWG copper — chart candidate

FAQ

Screen the published common sizes for copper or aluminum using a documented required load ampacity, overcurrent rating, insulation temperature, terminal limit and combined correction factor. This conservative comparison does not apply next-size-up, motor, parallel-conductor or dwelling-service exceptions. Aluminum sizes start at 8 AWG; missing chart cells are not filled in.

Use the exact equipment, dimensions, current ratings, operating conditions and applicable requirements described in the selected mode. Unknown values are not replaced by a generic wire, device count or capacity. Illustrative examples are arithmetic examples, not an approved installation.

Save planning case keeps an explicit local history entry. Copy MD retains current inputs, source notes and interpretation; Download CSV exports the current result breakdown. Export a separate copy before changing devices or clearing browser storage.

About Wire Gauge and Ampacity Selection

Screen the published common sizes for copper or aluminum using a documented required load ampacity, overcurrent rating, insulation temperature, terminal limit and combined correction factor. This conservative comparison does not apply next-size-up, motor, parallel-conductor or dwelling-service exceptions. Aluminum sizes start at 8 AWG; missing chart cells are not filled in.