SAFETY CRITICAL CALCULATION
Improper breaker sizing can cause fires, equipment damage, or electrical shock. This calculator provides guidance only. Always consult local electrical codes and hire a licensed electrician for installations.
Common Applications
Load Information
Full load current of the equipment
• Reference: NEC 210.3
If wire is already installed, check coordination
Sizing Results
Recommended Breaker
Load Calculation
Wire Coordination OK
AWG 12 wire is adequate for 20A breaker
Minimum Wire Size
Standard Breaker Sizes
🔴 Recommended • 🟢 Acceptable • ⚪ Too small
Calculation Steps
1. Load current: 20 A
2. Load type: general
3. System: 120V, 1-phase
4. NEC 210.3: 20 A × 1 (100%) = 20.0 A
5. Reason: Standard circuits, receptacles
6. Minimum breaker (next size up per NEC 240.6): 20 A
7. Minimum wire size (NEC 310.16): AWG 12 (25A capacity)
8. ✓ Specified wire AWG #12 (25A) is adequate
Formula
NEC Requirements
- • Wire ampacity ≥ breaker rating
- • Apply temperature derating
- • Apply grouping derating
- • Continuous load: 125% of load
- • Motor: 250% of FLC (NEC 430.52)
- • HVAC: 175% (locked rotor)
- • 14 AWG: max 15A breaker
- • 12 AWG: max 20A breaker
- • 10 AWG: max 30A breaker
Safety Notes
• Never use a breaker larger than wire ampacity
• Always follow local electrical codes
• Use GFCI/AFCI where required by code
• Label all circuits at panel
• Hire licensed electrician for installations