Breaker Size Calc NEC

NEC breaker size calculator for electricians, apprentices, and electrical engineers. Size overcurrent protection devices per NEC Article 240, with automatic continuous load adjustment, next-size-up rule, small conductor limits, and wire-breaker coordination. Works 100% offline on the job site.

Whether you're sizing a breaker for a 40A continuous lighting load, selecting overcurrent protection for an AC unit, or checking if a 14 AWG conductor needs a 15A breaker limit, this calculator gives you accurate NEC-compliant results in seconds. Use it as your go-to breaker sizing reference - from load analysis to conductor coordination.

BREAKER SIZE CALCULATOR FEATURES:
- All 36 standard overcurrent device ratings from 15A to 6000A per NEC 240.6(A)
- Automatic next-size-up breaker selection
- Continuous load 125% multiplier per NEC 210.20(A)
- Three load types: General, AC/Refrigeration (175%), Welder (200%)
- Small conductor protection limits per NEC 240.4(D): 14 AWG max 15A, 12 AWG max 20A, 10 AWG max 30A
- Wire-breaker coordination check per NEC 240.4
- Recommended conductor size from NEC Table 310.16 (75°C column)
- Copper and aluminum conductor support
- 6 voltage presets: 120V, 208V, 240V, 277V, 480V, 600V
- Single-phase and three-phase support
- NEC article references for every calculation result

NEC REFERENCES INCLUDED:
- NEC 240.6(A) - Standard overcurrent device ratings
- NEC 210.20(A) - Continuous load 125% rule
- NEC 240.4(B) - Next standard size up rule
- NEC 240.4(D) - Small conductor protection limits
- NEC 240.4 - Overcurrent protection of conductors
- NEC Table 310.16 - Conductor ampacity at 75°C

LOAD TYPE SUPPORT:
- General loads - 100% non-continuous, 125% continuous per NEC 210.20(A)
- AC/Refrigeration - 175% per NEC Article 440
- Welder - 200% per NEC 630.12

CALCULATION RESULTS INCLUDE:
- Recommended breaker size (standard rating per NEC 240.6(A))
- Adjusted load amps with multiplier explanation
- Recommended conductor size with ampacity from Table 310.16
- Breaker-to-wire ampacity verification
- Small conductor warnings when applicable
- Complete NEC article references for each result

PRO FEATURES (one-time purchase):
- No ads - clean interface for professionals
- Save breaker calculation history with labels
- Export calculations as PDF reports for permits and records
- Dark theme support

HOW THE BREAKER SIZE CALCULATOR WORKS:
1. Select