Standard Breaker Sizes NEC & Fuse Ratings
Free online tool • 2026 NEC Compliant
NEC Table 240.6(A) defines standard overcurrent protection device (breaker and fuse) ratings. When calculations result in non-standard ratings, the code generally allows rounding up to the next standard size. Use the breaker sizing calculator below, and reference the official standard amperage charts on this page.
Recommended Sizing
NEC Standard SizeBreaker Type: Standard Inverse-Time
NEC Reference Note: 125% multiplier applied for continuous loads per NEC 210.20(A).
How to Use This Calculator
Calculate circuit load
Sum continuous loads at 125% and non-continuous loads at 100%.
Find required ampacity
Select a conductor with an ampacity rating matching or exceeding the calculated load.
Compare to standard sizes
If the conductor ampacity does not match a standard size under 800A, round up to the next standard breaker rating.
Frequently Asked Questions
What are standard breaker sizes?
Per NEC 240.6(A), standard inverse-time circuit breaker ratings are 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 Amps. Additional standard fuse ratings include 1, 3, 6, and 10 Amps.
Can I round up to the next standard breaker size?
Yes. Under NEC 240.4(B), you can use the next standard overcurrent device rating (rounding up) if the calculated conductor ampacity does not correspond to a standard size, provided the rating does not exceed 800 amps and the circuit is not a multioutlet branch circuit.
Specific Sizing Guides & Calculators
Electric Range Circuit Breaker & Wire Size
What size breaker does an electric range need? Standard ranges require a 40A or 50A double-pole breaker on a dedicated 240V circuit per NEC.
Electric Water Heater Breaker & Wire Size
What size breaker does a water heater need? Standard 4500W electric water heaters require a 30A double-pole breaker with 10 AWG copper wire per NEC rules.
Electric Dryer Breaker & Wire Size
Standard electric dryers require a 30 amp double-pole breaker with 10 AWG copper wire on a 240V circuit. Learn how to size your dryer circuit.
3-Phase Circuit Breaker & Wire Size Calculator
Calculate 3-phase circuit breaker and wire size. Supports 208V, 240V, and 480V three-phase systems for motors, heaters, and continuous commercial loads.
Hot Tub & Spa Breaker Size (NEC Article 680)
What size breaker does a hot tub need? Most hardwired 240V spas require a 50 amp GFCI breaker with 6 AWG copper wire per NEC Article 680.
RV Breaker Size: 30 Amp vs 50 Amp Service
What size breaker for an RV outlet? 30A service uses a single-pole 120V breaker with 10 AWG wire; 50A service uses a double-pole breaker with 6 AWG wire.
Ductless Mini Split Breaker & Wire Size
What size breaker for a mini split AC unit? Sizing depends on the manufacturer's MCA/MOCP nameplate rating per NEC 440, typically 15A to 30A.
Built-In Electric Wall Oven Breaker & Wire Size
What size breaker for a built-in wall oven? Most single wall ovens need a 20A-30A double-pole 240V breaker; double wall ovens often require 30A-40A.
Garbage Disposal Breaker & Wire Size
What size breaker for a garbage disposal? Most residential disposals require a dedicated 15A or 20A 120V circuit with 14 or 12 AWG copper wire.
Submersible Well Pump Breaker & Wire Size
What size breaker for a well pump? Sizing depends on motor horsepower and full-load amps per NEC Article 430, typically 15A to 30A for residential pumps.
Dishwasher Breaker & Wire Size
What size breaker for a dishwasher? Most residential dishwashers need a dedicated 15A or 20A 120V circuit with GFCI protection per NEC 210.8(D).
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