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Circuit Load Calculator

By Muhammad Abdullah Rauf · Founder, EverydayTools.proUpdated 2026-03-01

How much load is on my circuit?

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.

Branch circuit load percent

Sums up to four watt loads, converts to amps at stated voltage, and compares to breaker rating.

Formula

Load % = (Σ watts ÷ volts) ÷ breaker amps × 100

Assumptions

  • Resistive loads at unity power factor.
  • Single-phase voltage as entered.

Limitations

  • Does not model motor inrush or power factor.
  • Not a panel schedule or NEC Article 220 load calc.

How to use Circuit Load Calculator

  1. List appliance watts

    Enter nameplate watts for each device on the same breaker (up to four).

  2. Enter circuit voltage

    120 V for standard branch circuits; 240 V for dryer/range circuits.

  3. Enter breaker size

    Read the breaker handle amps for that circuit.

  4. Read load percent

    Compare to 80% guidance for continuous loads; split circuits if overloaded.

Circuit Load Calculator examples

Kitchen loads

Input

1,500 + 800 W · 120 V · 20 A

Output

96% load

Single appliance

Input

1,200 W · 120 V · 20 A

Output

50% load

Who uses Circuit Load Calculator?

Common real-world scenarios where this tool saves time.

Kitchen 20 A check

1,500 W + 800 W → ~96% on 20 A — near capacity.

Garage 15 A circuit

1,200 W + 600 W → 15 A on 15 A breaker — full load.

Home office circuit

600 W + 400 W + 300 W on 15 A → ~11.7 A — ~78% load.

Workflow guides

Step-by-step chains that connect related tools for common tasks.

Before adding an outlet

  1. Sum existing loads here
  2. If under 80%, check wire gauge
  3. If over, plan new circuit with Breaker Sizing Calculator

Reference tables

Load percent guidance

Load %Typical meaningAction
Under 80%Headroom for continuous loadsGenerally acceptable for mixed use
80–100%Near capacityAvoid adding large appliances
Over 100%Overload riskSplit loads or upgrade circuit

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Frequently Asked Questions

What is the 80% rule for circuits?

For continuous loads, NEC suggests loading branch circuits to 80% of breaker rating — 16 A max on a 20 A breaker.

Can I add a 1,500 W microwave to a full circuit?

If load percent is already above 80%, adding appliances risks nuisance trips or overheating — split to a new circuit.

How do I find appliance watts?

Check the nameplate label on the cord or manual — watts or amps × volts.

Is 100% load safe on a breaker?

Brief peaks may trip a breaker; continuous loads should stay near or below 80% of breaker rating.

How many watts on a 20 amp circuit?

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.

Privacy, accuracy, and trust

Privacy

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.

Part of Calculator Tools

More free tools for the same workflow.

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Reviewed on 2026-03-01.