Breaker Sizing is a Pro feature
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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.
LOAD INFORMATION
A
Full load current of the equipment
• Standard circuits, receptacles
• Reference: NEC 210.3
• Reference: NEC 210.3
If wire is already installed, check coordination
COMMON APPLICATIONS
SIZING RESULTS
Recommended Breaker
20 A
Based on 20.0 A adjusted load
Minimum Wire Size
AWG 12
For 20A breaker @ 75°C copper
Load Calculation
Base Load Current:20 A
Load Type Factor:100%
Reference:NEC 210.3
Adjusted Load:20.0 A
Wire Coordination OK
AWG 12 wire is adequate for 20A breaker
Standard Breaker Sizes
15A
20A
25A
30A
35A
40A
45A
50A
60A
70A
80A
90A
100A
110A
125A
150A
175A
200A
225A
250A
RecommendedAcceptableToo small
Calculation Steps
- 01Load current: 20 A
- 02Load type: general
- 03System: 120V, 1-phase
- 04NEC 210.3: 20 A × 1 (100%) = 20.0 A
- 05Reason: Standard circuits, receptacles
- 06Minimum breaker (next size up per NEC 240.6): 20 A
- 07Minimum wire size (NEC 310.16): AWG 12 (25A capacity)
- 08✓ Specified wire AWG #12 (25A) is adequate
FormulaBreaker ≥ Load (NEC 210.3)
REFERENCE — NEC REQUIREMENTS
NEC 210.19(A) - Conductor Sizing
- • Wire ampacity ≥ breaker rating
- • Apply temperature derating
- • Apply grouping derating
NEC 210.20 - Overcurrent Protection
- • Continuous load: 125% of load
- • Motor: 250% of FLC (NEC 430.52)
- • HVAC: 175% (locked rotor)
NEC 240.4(D) - Small Conductors
- • 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