Electrical Wire Size Guide: Which Gauge Do I Need?

AWG Wire Sizing Basics

The American Wire Gauge (AWG) system rates wire by diameter — the lower the number, the thicker the wire and the more current it can safely carry. Residential wiring typically uses 14, 12, 10, 8, 6, and 4 AWG.

14 AWG handles 15 amps: used for general lighting circuits and low-draw receptacles. This is the minimum wire size allowed in residential construction.

12 AWG handles 20 amps: the standard for kitchen, bathroom, and garage receptacles. Most modern codes require 12 AWG for all general-purpose receptacles.

10 AWG handles 30 amps: used for dryers, water heaters, and window air conditioners. Typically paired with a 30-amp breaker.

6 AWG handles 55 amps: used for ranges, ovens, and large AC units. Requires special connectors and is significantly harder to work with due to stiffness.

Voltage Drop and Long Runs

Voltage drop is the loss of electrical pressure over distance. Code requires that total voltage drop not exceed 3% for branch circuits or 5% combined for feeder and branch circuits.

For a 120V circuit, 3% voltage drop is only 3.6 volts. Over a 100-foot run with 12 AWG wire carrying 20 amps, the voltage drop would be about 3.2% — right at the limit.

For long runs (over 50 feet), you often need to upsize the wire by one gauge. For example, use 10 AWG instead of 12 AWG for a 20-amp circuit running 75-100 feet to the load.

Our electrical wire calculator computes voltage drop for your specific run length, amperage, and wire gauge, telling you if you need to upsize.

Common Home Circuits

Kitchen small appliance circuits: two 20-amp circuits minimum (12 AWG), serving countertop receptacles. Dishwasher and garbage disposal each need their own dedicated circuit.

Bathroom circuits: at least one 20-amp GFCI-protected circuit (12 AWG). Many homes now use one dedicated circuit per bathroom for convenience.

Laundry room: one 20-amp circuit for the washing machine (12 AWG) and a separate 30-amp circuit for a gas dryer or 40-50 amp for an electric dryer.

Outdoor circuits and pools: must be GFCI protected. Pools require specific wire sizing based on pump motor amperage and distance from the electrical panel. Always consult a licensed electrician for pool wiring.

Safety and Code Requirements

Always match wire gauge to the breaker size. Never put 14 AWG wire on a 20-amp breaker — the wire can overheat before the breaker trips, creating a fire hazard.

Use the correct wire type for the location: NM-B (Romex) for dry indoor locations, UF-B for underground burial, THWN/THHN for conduit runs, and MC cable for exposed commercial installations.

Electrical work requires permits and inspections in most jurisdictions. Even if your area allows homeowner electrical work, having it inspected protects your home insurance coverage and resale value.

When in doubt, hire a licensed electrician. Electrical mistakes can cause fires, electrocution, and code violations that are expensive to remediate. The cost of professional installation is modest compared to the risks.