Quick answer
Electrical wire gauge is the size of a metal conductor, stated in the US as an American Wire Gauge (AWG) number, where a smaller number means a thicker wire that can carry more current safely.
Gauge sets how many amps a wire may carry, which breaker can protect it and how much voltage it loses over distance. Home branch circuits mostly use 14, 12 and 10 AWG copper.
Quick facts
The key facts about Electrical Wire Gauge, with sources:
- US system
- American Wire Gauge (AWG); sizes above 4/0 are stated in kcmil
- Rule of thumb
- Lower number = thicker wire = more amps
- 14 AWG copper, 60°C column
- 15 amps 1
- 12 AWG copper, 60°C column
- 20 amps 1
- 10 AWG copper, 60°C column
- 30 amps 1
- Code that governs it
- NFPA 70, the National Electrical Code (ampacity table and small-conductor rule) 4
- Where it is printed
- On the cable jacket or the wire insulation, every few feet 3
Key takeaways
- Wire gauge is the thickness of the metal inside a wire, and in the US it is stated as an AWG number.
- The scale runs backward: 10 AWG is thicker than 12 AWG, and 12 AWG is thicker than 14 AWG.
- A thicker wire can carry more amps before it gets too hot, so gauge and breaker size must match.
- In common home copper wire, 14 AWG pairs with a 15-amp breaker and 12 AWG with a 20-amp breaker 1.
- Aluminum wire needs a larger size than copper for the same load 3.
What wire gauge means
Every wire in a home has a metal core, called the conductor. Gauge is the size of that core. It is not the size of the plastic around it. Two wires with the same gauge can look different if one has thicker insulation.
The US uses the American Wire Gauge system, or AWG. The numbers count down as the wire gets thicker.
That is why a 10 AWG wire for a water heater is fatter than the 14 AWG wire on a bedroom light circuit.
Above 4/0 (said "four aught"), sizes switch to kcmil, which means thousands of circular mils, a unit of area.
The search term "American Wire Gauge" and the term "wire gauge" mean the same thing on a US job. This page covers both. If a quote, cable label or inspection report says "12 AWG", "#12" or "12-gauge", it is the same size.
Gauge is not the same as ampacity
Gauge is a physical size. Ampacity is how many amps that size may carry under set conditions. One gauge can have several ampacity values, depending on the metal, the insulation temperature rating and how the wire is installed.
How gauge controls heat, current and voltage
Current moving through a wire meets resistance, and resistance turns some energy into heat. A thicker wire has less resistance per foot, so it runs cooler at the same current. That is the whole reason gauge matters.
Insulation can only take so much heat. Wire is rated by the top temperature its insulation can stand, such as 60°C, 75°C or 90°C. The NEC ampacity table lists how many amps each size may carry in each temperature column 1.
The lowest-rated part of the circuit, often the device terminal, sets the column that applies.
Gauge also sets voltage drop. On a long run, a thin wire wastes more voltage as heat, so motors and chargers at the far end see less than full voltage. Electricians sometimes pick one size up for distance, not for heat. You can see the effect with the voltage drop calculator.
- Know the loadamps the circuit will carry
- Pick the metalcopper or aluminum
- Find the temperature columnset by insulation and terminals
- Read the ampacityNEC Table 310.16
- Apply limitssmall-conductor rule, derating, distance
- Match the breakerbreaker protects the wire
Common home wire sizes and typical uses
Six copper sizes cover most of the cable printed in a house. Ampacity values come from a manufacturer chart built on the NEC table and do not include derating 1.
| Copper size | Ampacity at 60°C | Ampacity at 75°C | Typical home use |
|---|---|---|---|
| 14 AWG | 15 A | 20 A | General lighting and outlet circuits on a 15-amp breaker |
| 12 AWG | 20 A | 25 A | Kitchen, bath, laundry and garage outlet circuits on a 20-amp breaker |
| 10 AWG | 30 A | 35 A | Many water heaters, some dryers and window AC units |
| 8 AWG | 40 A | 50 A | Some ranges, cooktops and larger AC units |
| 6 AWG | 55 A | 65 A | Ranges, some EV charger circuits, subpanel feeders |
| 4 AWG and larger | 70 A and up | 85 A and up | Feeders, service conductors |
Sources: [1]
Worked example: why a 20-amp circuit needs 12 AWG
A 20-amp kitchen outlet circuit makes a good test case. The numbers below are published table values, worked through for reading a quote or label, not for designing a circuit.
| Step | What you check | Result |
|---|---|---|
| 1 | Breaker on the circuit | 20 amps |
| 2 | Copper 14 AWG at 60°C | 15 amps, too small 1 |
| 3 | Copper 12 AWG at 60°C | 20 amps, matches 1 |
| 4 | Copper 12 AWG at 90°C (THHN in conduit) | 30 amps in the table, yet still capped at 20 amps of breaker by the NEC small-conductor rule |
| 5 | Answer | 12 AWG copper on a 20-amp breaker |
Step 4 is the trap. A higher temperature rating raises the table number, but the small-conductor rule in NEC 2023 Section 240.4(D) still limits 12 AWG copper to 20-amp protection. That is why a 30-amp breaker on 12 AWG wire is a red flag in any inspection.
Where you will see the gauge
On plastic-sheathed cable, the size is printed on the outer jacket, along with the number of wires and the cable type, such as "12-2 W/G". The first number is gauge.
The second is the count of insulated wires. "W/G" means with ground. CPSC notes these markings repeat every few feet and can be read in unfinished basements, attics and garages 3.
Newer NM-B cable also uses jacket color to signal size: white for 14 AWG, yellow for 12 AWG and orange for 10 AWG on one major brand 2. Color is a convenience, not a rule, so the printed size is what counts.
Single wires such as THHN in conduit carry the size on the insulation. On a quote, the gauge appears next to the circuit, for example "run new 6 AWG copper for 50 A EV circuit". On the panel, the breaker handle shows the amps the wire must be able to carry.
Why the right gauge pays off
- Less heat. Wire sized to the load runs within its insulation rating, which slows aging.
- Breakers work as designed. A circuit breaker only protects a wire it is sized for.
- Full voltage at the far end. Larger wire on long runs keeps motors and chargers within their rated voltage.
- Room to grow. A heavier feeder now can save pulling new wire when a load is added later.
- Cleaner inspections. Mismatched wire and breakers are a common write-up on an electrical inspection.
What gauge alone does not tell you
Gauge tells you
- The size of the conductor.
- A starting point for ampacity in the NEC table.
- Whether a wire looks right for the breaker it sits on.
Gauge does not tell you
- Whether the metal is copper, aluminum or copper-clad aluminum. Read the jacket.
- The insulation temperature rating, which changes the table column.
- Derating for heat, bundling or many wires in one conduit.
- Whether the run is long enough to need upsizing for voltage drop.
- Whether the connection points are rated for the metal used.
What drives the cost of wire size
Larger gauge means more metal per foot, so heavier wire costs more to buy and takes more labor to pull and terminate. The size step from 12 to 10 AWG matters little on one short run but adds up on a full rewire or a long feeder to a garage.
Other drivers are copper versus aluminum, conduit versus cable, how far the run goes, how many walls and floors it crosses and whether drywall must be opened.
We do not publish per-foot prices here, because metal prices move and a figure without a dated source would mislead. See what electrical work costs or estimate a job with the project cost tool.
Lifespan depends on heat and connections more than gauge. Wire that runs cool, with tight, rated terminations, tends to last. Manufacturer warranties cover the product, not the installation.
How an electrician sizes and installs wire
Wire sizing on a permitted job follows the same six checks every time. Knowing them helps you follow a quote; they are not a guide to doing the work yourself.
- Calculate the load: the electrician lists what the circuit will power and its amps.
- Choose the metal and wiring method: cable such as NM-B in dry walls, or single wires in conduit.
- Read the ampacity table for that metal and temperature column, then apply any derating.
- Check the NEC small-conductor rule and the device terminal ratings.
- Check distance and upsize for voltage drop if needed.
- Pull the permit where your jurisdiction requires one, install, and pass inspection.
- Wire size for each new circuit
- Copper or aluminum
- Breaker size that matches the wire
- Run length if it is long
- Permit and inspection included
Permits and inspections vary by city and state. Our guide to electrical permits explains when one is needed.
Keeping wire healthy
Wire inside walls needs no routine care. The weak points are the ends: outlets, switches, splices and breaker lugs. Heat there builds over years, especially where a connection has loosened.
What you can do is limited and safe: notice warm cover plates, flickering lights, buzzing or a burning smell, and avoid running heaters on extension cords. A periodic inspection by a licensed electrician is the right way to check terminations. Older homes with mixed wire types benefit most.
Warning signs of undersized wire
Safety and risk
A breaker larger than the wire it protects can let that wire overheat without tripping.
Hot outlet covers, scorched plugs, a smell of melting plastic or lights that dim when a load starts are reasons to stop using the circuit and call a licensed electrician.
If you see smoke or flame, leave and call 911. Never swap a breaker for a bigger one to stop nuisance trips.
Common gauge problems found in homes
- 14 AWG wire on a 20-amp breaker, often after someone "fixed" a tripping circuit.
- An appliance moved to a circuit sized for a smaller load.
- Long runs to a shed or garage using wire sized only for heat, not distance.
- Aluminum branch wiring treated as if it were copper of the same size 3.
- Extension cords used as permanent wiring, often too thin for the load.
If any of these sounds familiar, our home electrical safety check walks through the warning signs.
The rules that set wire size
Wire sizing in US homes is governed by NFPA 70, the National Electrical Code 4. The 2023 edition lists conductor ampacity in Table 310.16 (numbered 310.15(B)(16) in older editions).
Section 240.4(D) caps overcurrent protection for small copper conductors at 15 amps for 14 AWG, 20 amps for 12 AWG and 30 amps for 10 AWG, unless another section allows otherwise. NFPA offers free read-only access to its codes online 5.
The NEC is a model code. Each state or city adopts an edition, sometimes with local changes, so the edition that applies to your home depends on where you live 6. Check yours with the NEC edition lookup. Workplaces also fall under OSHA electrical rules.
Wire gauge compared with related terms
| Term | What it describes | How it links to gauge |
|---|---|---|
| Wire gauge (AWG) | Size of the conductor | The starting point |
| Ampacity | Safe current for a size under set conditions | Read from the gauge in the NEC table |
| Amperage | Current actually flowing | Must stay within the ampacity |
| THHN / NM-B | Insulation or cable type | Sets the temperature column used |
| Aluminum wire | Conductor metal | Needs a larger gauge than copper for the same load |
| Branch circuit | Circuit from breaker to outlets | Its breaker size sets the minimum gauge |
Myths about wire gauge
- Myth A bigger number means a bigger wire.
- Reality The reverse. In AWG, 10 is thicker than 14.
- Myth If a breaker keeps tripping, install a bigger one.
- Reality The breaker protects the wire. Upsizing it without upsizing the wire removes that protection.
- Myth 90°C wire can always run at its 90°C ampacity.
- Reality Terminals, the cable type and the small-conductor rule often cap it lower 1.
- Myth Jacket color tells you the size for sure.
- Reality Color coding is a brand convention. The printed size is what counts 2.
- Myth Aluminum and copper of the same gauge are interchangeable.
- Reality Aluminum carries less current at the same size and needs rated connectors 3.
How rules differ by state
Wire gauge physics is the same everywhere, but the code edition is not. States and cities adopt the NEC on their own schedule, and NFPA tracks where each edition is enforced 6. Who may install wire also depends on state licensing tiers. Check your state before a job.
When wire gauge matters to you
Gauge matters most when you add a big load: an EV charger, heat pump, hot tub, range or subpanel. Each needs wire sized for its circuit, and the existing wire may not qualify. It also matters when buying an older home with unknown work.
Start by noting the breaker sizes in your panel, list the new loads you want, and ask a licensed electrician to confirm the wire sizes on the quote. The wire size calculator shows what size a load usually needs.
- If Adding a 240-volt appliance or EV charger
- Then Yes: new circuit, wire sized for it
- If Breaker trips often on one circuit
- Then Have an electrician check load and wire, not the breaker
- If Home built 1965 to mid-1970s
- Then Check for aluminum branch wiring
- If Long run to a garage or shed
- Then Ask about voltage drop upsizing
Source: [3]
Tools and guides
- Appliance circuit lookupTypical breaker and wire per appliance
- Electrical load calculatorWill new loads fit your service?
- Whole-house rewiringWhen old wire needs replacing
Questions about Electrical Wire Gauge
What gauge wire do I need for a 20-amp circuit?
A 20-amp circuit in a home normally needs 12 AWG copper wire. The NEC small-conductor rule limits 14 AWG copper to 15-amp protection, so it cannot be used on a 20-amp breaker.
Long runs may call for 10 AWG to limit voltage drop. Aluminum wire would need a larger size. An electrician confirms the size for your run and load.
Is 12 gauge or 14 gauge wire thicker?
12 gauge wire is thicker than 14 gauge. In the American Wire Gauge system the numbers go down as the wire gets bigger.
That backward scale comes from the old wire-drawing process, where each pass through a die made the wire thinner.
So 10 AWG is thicker still, and 4/0 is far thicker than any branch circuit wire.
What does AWG stand for?
AWG stands for American Wire Gauge, the standard US system for sizing round electrical conductors. It applies to solid and stranded copper and aluminum. Sizes larger than 4/0 are stated in kcmil instead. When a cable says "12 AWG" or a quote says "#12", both refer to the same AWG size.
How many amps can 14 gauge wire handle?
Fourteen-gauge copper wire is limited to 15 amps of breaker protection on a typical home circuit.
The NEC table lists 15 amps in the 60°C column and higher values in the 75°C and 90°C columns, but the small-conductor rule caps protection at 15 amps for most uses.
That is why 14 AWG appears on 15-amp lighting and outlet circuits.
What gauge wire is used for an electric range or dryer?
Dryers usually take 10 AWG copper and ranges 8 or 6 AWG copper, but the appliance nameplate and breaker size decide. Many dryers use a 30-amp circuit, which points to 10 AWG copper.
Ranges often use 40 or 50 amp circuits, which point to 8 or 6 AWG copper. The installation manual sets the requirement. The appliance circuit lookup tool shows typical pairings.
Does a longer wire run need thicker wire?
Often, yes. Wire has resistance, and on long runs it loses voltage along the way. The NEC table sets size by heat, not distance, so electricians check voltage drop separately and may go one or two sizes larger. This matters for detached garages, wells and EV chargers far from the panel.
Is aluminum wire a different gauge than copper?
Aluminum is sized larger than copper for the same load. CPSC notes that aluminum branch circuits were sized at 12 AWG for 15-amp circuits and 10 AWG for 20-amp circuits, compared with 14 and 12 AWG for copper.
Aluminum also needs connectors and devices rated for it. If a home from the late 1960s shows 12 AWG wire on 15-amp breakers, ask an electrician whether it is aluminum.
Can I use thicker wire than required?
Yes, a larger wire than the minimum is allowed and runs cooler, as long as it fits the terminals and the box.
It costs more and can be harder to bend into devices. The breaker still has to match the load and the smallest wire on the circuit. An electrician can confirm terminals accept the larger size.
How do I find the wire gauge in my house?
Look at the printed markings on cable jackets in an unfinished basement, attic or garage. The marking shows the size, the number of conductors and the metal. Do not open panels or boxes to look.
If wiring is hidden, a licensed electrician can identify it during an inspection. The breaker label on each handle tells you the amps the wire is meant to carry, which is a good starting clue.
What gauge wire does an EV charger need?
A Level 2 charger needs wire sized for its breaker, which is set by the charger rating. Chargers are continuous loads, so the circuit is sized at 125% of the charging current. A 40-amp charger on a 50-amp circuit often uses 6 AWG copper. The charger manual and the electrician set the exact size.
Sources
- Cerrowire, Ampacity Charts (wire size and amp ratings, based on the 2017 NEC), retrieved .
- Cerrowire, CerroMax NM-B product page, retrieved .
- U.S. Consumer Product Safety Commission, Publication 516: Repairing Aluminum Wiring (June 2011), retrieved .
- NFPA, NFPA 70 (National Electrical Code) code development page, retrieved .
- NFPA, Free access to NFPA codes and standards, retrieved .
- NFPA, Where the NEC is enforced (adoption maps), retrieved .
Expert review
Written by the HyreElectrical Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Ampacity values read from the manufacturer chart; NEC sections named by edition; CPSC publication read in full. No prices published (G-COST).
Suggest a correction. We fix errors and say what changed.