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Circuit Breaker Size Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.

Formel

Breaker Size = Load Watts / Voltage × 1.25 (125% NEC rule)

Trin-for-trin guide

  1. 1Calculate total load in watts, divide by voltage, multiply by 1.25
  2. 2Apply the formula using your project measurements
  3. 3Add required safety factors or waste allowances per code

Løste eksempler

Input
2400W load, 120V circuit
Resultat
Breaker = 2400/120 × 1.25 = 25A → use 30A breaker

Almindelige fejl at undgå

  • Not applying code-required safety factors or derating
  • Forgetting to account for waste and cut losses in material estimates

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