What is the 80% rule for circuits?
Continuous loads should stay at or below 80% of breaker rating — 16 A max on a 20 A breaker.
Branch circuit load is the **sum of connected watts** divided by **circuit voltage**.
**Formula:**
Total amps = (Load₁ + Load₂ + …) ÷ Volts
Load % = Total amps ÷ Breaker amps × 100
**Example — kitchen circuit:**
Microwave 1,500 W + toaster 800 W = **2,300 W**
2,300 ÷ 120 V = **19.2 A**
On a **20 A breaker** → **96% load**
NEC guidance suggests staying at or below **80%** for continuous loads. This tool flags high percentages — it does not certify code compliance.
Concise answers for common searches — definitions, steps, and comparisons.
Continuous loads should stay at or below 80% of breaker rating — 16 A max on a 20 A breaker.
Sums up to four watt loads, converts to amps at stated voltage, and compares to breaker rating.
Formula
Load % = (Σ watts ÷ volts) ÷ breaker amps × 100Enter nameplate watts for each device on the same breaker (up to four).
120 V for standard branch circuits; 240 V for dryer/range circuits.
Read the breaker handle amps for that circuit.
Compare to 80% guidance for continuous loads; split circuits if overloaded.
Input
1,500 + 800 W · 120 V · 20 AOutput
96% loadInput
1,200 W · 120 V · 20 AOutput
50% loadCommon real-world scenarios where this tool saves time.
1,500 W + 800 W → ~96% on 20 A — near capacity.
1,200 W + 600 W → 15 A on 15 A breaker — full load.
600 W + 400 W + 300 W on 15 A → ~11.7 A — ~78% load.
Step-by-step chains that connect related tools for common tasks.
| Load % | Typical meaning | Action |
|---|---|---|
| Under 80% | Headroom for continuous loads | Generally acceptable for mixed use |
| 80–100% | Near capacity | Avoid adding large appliances |
| Over 100% | Overload risk | Split loads or upgrade circuit |
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For continuous loads, NEC suggests loading branch circuits to 80% of breaker rating — 16 A max on a 20 A breaker.
If load percent is already above 80%, adding appliances risks nuisance trips or overheating — split to a new circuit.
Check the nameplate label on the cord or manual — watts or amps × volts.
Brief peaks may trip a breaker; continuous loads should stay near or below 80% of breaker rating.
At 120 V, a 20 A circuit can supply up to 2,400 W at 100% — use 80% (1,920 W) as a continuous-load guide.
Appliance watt totals are processed only in your browser — EverydayTools does not store circuit load inputs.
Branch load estimate only — not a NEC Article 220 panel schedule or licensed electrical assessment.
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Reviewed on 2026-03-01.
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