How to read the result
A breaker’s capacity is its amp rating times the circuit voltage — a 15-amp, 120-volt circuit can carry 1,800 watts before it trips. But the electrical code treats 80% as the working limit for continuous loads (anything running three hours or more), which puts the real-world budget for that 15-amp circuit at 1,440 watts. This calculator totals the wattage you add, converts it to amps, and grades the circuit against both lines: green means comfortable, amber means you’re past the 80% continuous-load limit, and red means the total exceeds the breaker rating — the load that trips breakers and, with worn connections, overheats wiring.
Why this matters more than people think
The classic overload isn’t exotic: it’s a space heater (1,500 W) and a hair dryer (1,800 W) meeting on the same 15-amp bedroom circuit that also feeds the TV. Nothing is “broken” — the circuit is simply being asked for more than it can deliver, and the breaker is doing its job by tripping. A breaker that trips repeatedly, an outlet that’s warm to the touch, or a faint burning smell are all signals to redistribute load first and investigate second. Our guides on a sparking outlet, a dead light switch, and flickering kitchen lights walk through the safe diagnostic steps for each symptom.
Safety rules that override any calculator
- Never replace a breaker with a larger one to stop it tripping. The breaker is sized to protect the wire in the wall, not your appliances. Upsizing it removes that protection and is a genuine fire risk.
- Work inside the electrical panel is not DIY. Identifying which outlets share a circuit (flip breakers, see what goes dark) is safe; anything beyond the panel cover belongs to a licensed electrician.
- Nameplate watts beat estimates. The presets here are typical figures; the label on your actual appliance is the authoritative number — use the custom field with it when precision matters.
- Motors and compressors draw a brief surge above their running watts at startup; if a circuit sits near the line, that surge is what trips it. Read our disclaimer — this tool gives estimates for planning, not an electrical inspection.
Frequently asked questions
How do I find out which outlets are on one circuit?
Turn off one breaker at a time and note what loses power — label the panel as you go. Ten minutes of mapping saves every future overload guess.
What if my total is fine but the breaker still trips?
Either a startup surge from a motor, a failing appliance drawing more than its rating, or a worn breaker. Unplug devices one at a time to isolate it; if a near-empty circuit still trips, bring in an electrician.
Is anything I enter saved?
No — everything runs in your browser and nothing is stored or transmitted.