Appliance Load & Circuit Capacity Calculator
Calculate the total electrical load of your appliances and check whether your circuit can safely handle them. Enter your circuit breaker size, voltage, and up to 8 appliances.
Appliances
Enter wattage (W) or amperage (A) for each appliance. Leave unused rows blank.
| Appliance Name | Watts (W) | — OR — Amps (A) | Qty |
|---|
Formulas Used
Power (W) from Amps: W = A × V
Amps from Watts: A = W ÷ V
Total Load (W): Σ (Watts × Quantity) for all appliances
Total Load (A): Total W ÷ V
Circuit Capacity (W): Breaker (A) × V
Safe Load Limit (80% Rule): Safe W = Circuit Capacity × 0.80
Headroom: Safe W − Total Load W
The NEC 80% rule states that a circuit should not be loaded beyond 80% of its rated capacity for continuous loads (loads running 3+ hours).
Assumptions & References
- Voltage is assumed constant at the selected value (120 V or 240 V).
- Power factor is assumed to be 1.0 (purely resistive loads). Inductive loads (motors, compressors) may draw more current.
- The 80% continuous load rule is per NEC Article 210.20(A) and NEC 384.16.
- Circuit breaker size refers to the rated amperage of the breaker protecting the circuit.
- Startup (inrush) current for motors can be 3–7× running current — consult an electrician for motor-heavy circuits.
- This calculator is for estimation purposes only. Always consult a licensed electrician for actual installations.
- Reference: NFPA 70 National Electrical Code (NEC), 2023 Edition.