calc.engineer / Solar & Power / Wire Ampacity

Wire Ampacity v1.0.0

Determine minimum wire gauge using NEC Table 310.16 ampacity ratings with full derating. Looks up base ampacity for copper or aluminum conductors at 60°C, 75°C, or 90°C insulation rating, then applies NEC 310.15(C)(1) ambient temperature correction and NEC 310.15(C)(2) conductor count adjustment. Automatically applies the 125% continuous load factor per NEC 210.20(A) when flagged. Returns the minimum AWG that meets the derated requirement, plus a comparison table of all gauges. Different from wire_gauge which focuses on voltage drop — use both together for complete wire sizing. Essential for residential panels, commercial feeders, solar arrays, and EV charging installations.

← from wire_gauge.current_amps← from solar_sizing.current_ampsfeeds wire_gauge →
Required circuit current in amperes. Use 125% of continuous load per NEC 210.20(A).
Conductor material. Copper has higher ampacity; aluminum is lighter and cheaper for large feeders.
Insulation temperature rating in °C. 60=TW/UF-B, 75=THW/THWN/XHHW (most common), 90=THHN/THWN-2.
Ambient temperature in °C. NEC base is 30°C. Higher temps require derating. Typical: 30 (indoor), 40 (attic/hot), 45+ (rooftop conduit).
Number of current-carrying conductors in a single raceway or cable. More than 3 requires derating per NEC 310.15(C)(2).
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/wire_ampacity \
  -H "Content-Type: application/json" \
  -d '{"current_amps": …, "conductor": …, "insulation": …}'

MCP: connect to https://calc.engineer/mcp and call wire_ampacity.

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