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Breaker Sizing Calculator

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

What size breaker do I need?

Breaker sizing starts with **load amps = Watts ÷ Volts**. For **continuous loads**, multiply by **1.25**, then pick the **next standard breaker** that meets or exceeds that value.

**Standard sizes:** 15, 20, 25, 30, 35, 40, 50, 60 A (and higher)

**Example — 5,500 W electric dryer at 240 V:**

5,500 ÷ 240 = **22.9 A**

22.9 × 1.25 = **28.6 A design**

Next standard breaker: **30 A**

Minimum wire: **10 AWG** copper (30 A ampacity)

Breaker rating must not exceed wire ampacity. This calculator pairs recommended wire with breaker size.

Quick answers

Concise answers for common searches — definitions, steps, and comparisons.

What breaker for a 240V dryer?

Most residential dryers use a 30 A double-pole breaker on 10 AWG copper.

Standard breaker selection

Converts watts to amps, applies continuous factor, selects next standard breaker and matching minimum copper wire.

Formula

Design amps = (Watts ÷ Volts) × 1.25 if continuous → next standard breaker ≥ design amps

Assumptions

  • Single-phase resistive load.
  • Standard US breaker sizes.
  • Copper NM-B 60°C wire pairing.

Limitations

  • Does not replace permit, inspection, or local code amendments.
  • Motor circuits need separate starting-current analysis.

How to use Breaker Sizing Calculator

  1. Enter appliance watts

    Use nameplate watts for the largest load on the new circuit.

  2. Enter circuit voltage

    120 V for general branch; 240 V for dryer, range, and water heater.

  3. Set continuous load

    Enable for dryers, ranges, and equipment that runs 3+ hours at full load.

  4. Read breaker and wire

    Result shows standard breaker size and minimum matching copper wire gauge.

Breaker Sizing Calculator examples

Dryer circuit

Input

5,500 W · 240 V · continuous

Output

30 A breaker

Window AC

Input

1,200 W · 120 V

Output

15 A breaker

Who uses Breaker Sizing Calculator?

Common real-world scenarios where this tool saves time.

Electric dryer

5,500 W at 240 V continuous → 30 A breaker, 10 AWG.

Window AC

1,200 W at 120 V non-continuous → 15 A breaker, 14 AWG.

Electric range

8,000 W at 240 V → 40 A breaker, 8 AWG.

Workflow guides

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

New appliance circuit

  1. Size breaker here
  2. Confirm wire in Wire Gauge Calculator
  3. Check circuit load if sharing a panel slot

Reference tables

Standard residential breaker sizes

BreakerTypical useMin copper wire
15 AGeneral 120 V outlets14 AWG
20 AKitchen, bath, workshop12 AWG
30 ADryer, small water heater10 AWG
40 ARange, large appliances8 AWG

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Frequently Asked Questions

What breaker for a 240V dryer?

Most residential dryers need a 30 A double-pole breaker on 10 AWG copper — confirm nameplate amps on your model.

Can breaker be larger than wire allows?

No — breaker must protect wire ampacity. This calculator shows minimum wire for the recommended breaker.

15 or 20 amp outlets?

General 120 V branch circuits use 15 A (14 AWG) or 20 A (12 AWG) breakers — match wire gauge to breaker.

What breaker for a 5,500 W dryer?

At 240 V continuous load, 5,500 W draws ~22.9 A — use a 30 A breaker with 10 AWG copper minimum.

Does a 20 A breaker need 12 AWG wire?

Yes — 20 A breakers require at least 12 AWG copper NM-B; 14 AWG is only rated for 15 A circuits.

Privacy, accuracy, and trust

Privacy

Appliance watts and voltage are processed only in your browser — EverydayTools does not store circuit inputs.

Estimate only — not NEC certification or permit approval. Licensed electricians required for new circuits.

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Reviewed on 2026-03-01.

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