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Box Fill Calculator

Calculate electrical box fill per NEC Article 314.16. Includes conductors, equipment grounds, clamps, and device allowances.

Based on NEC 2023 Article 314.16

Professional Verification Required

This calculator provides estimates for reference purposes only. Results must be verified by a licensed electrician or electrical engineer before any installation.

  • Local codes and AHJ requirements may differ from NEC standards
  • Site conditions, temperature, and installation methods affect sizing
  • Always verify ampacity, derating factors, and conductor sizing in the field

NEC Reference: NEC 2023 Article 314.16

Box Configuration

Click a preset to auto-fill, or configure manually below

or customize
NEC 314.16(B) Rules: Count each conductor as 1×. All grounds together count as 1×. All clamps together count as 1×. Each device/yoke counts as 2×.
NEC 314.16 Quick Reference

Volume Allowances (in³)

#14 AWG:2.00#12 AWG:2.25#10 AWG:2.50#8 AWG:3.00

Counting Rules

  • Each conductor = 1× volume
  • All grounds together = 1×
  • All clamps together = 1×
  • Each device/yoke = 2×

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⚠️ IMPORTANT LEGAL DISCLAIMER

For Reference Only: This calculator is provided for educational and informational purposes only. It is not intended to be a substitute for professional engineering design, advice, or certification.

Code Compliance: Calculations are based on the 2023 National Electrical Code (NEC®). However, local codes, amendments, and Authority Having Jurisdiction (AHJ) requirements vary by location and may supersede standard NEC requirements.

No Liability: SparkShift and its affiliates assume no liability for errors, omissions, or the use/misuse of this tool. Users are solely responsible for verifying all results against applicable codes and standards before installation. Always consult a licensed electrician or engineer.

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