50 Amp Wire Size

The wire size for a 50 amp breaker is 6 AWG copper in NM-B or UF-B cable, and 8 AWG copper in conduit where every termination is listed 75°C. Both are correct; they answer the same question under different wiring methods, and the method is what decides.

50 Amp Wire Size in Copper

8 AWG copper is rated 50 amps in the 75°C column of NEC Table 310.16. That equals a 50 amp load exactly, with no margin at all. It is legal — an ampacity equal to the load satisfies the code — and it is the answer only where the 75°C column applies, which means individual conductors in a raceway landing on terminations listed for 75°C.

6 AWG copper is rated 55 amps at 60°C, 65 at 75°C and 75 at 90°C. It clears 50 amps in every column, which is why it is the answer that never needs qualifying.

The difference between the two is not a matter of preference. It is NEC 110.14(C): the ampacity must be read in the column matching the lowest-rated termination in the circuit. A conductor rated 90°C landing on a 75°C lug is a 75°C circuit, and inside NM-B cable it is a 60°C circuit whatever the conductors are individually rated.

50 Amp Wire Size in Aluminum

6 AWG aluminum is rated 50 amps at 75°C. Like 8 AWG copper, it meets a 50 amp load exactly and no more.

Aluminum is more realistic at 50 amps than it is at smaller sizes. 6 AWG is a size aluminum is commonly stocked in for feeders, and a 50 amp feeder to an outbuilding is exactly the run where aluminum's cost and weight advantages start to matter. 8 AWG aluminum is not an option at this amperage — it is rated 40 amps.

The zero margin is the thing to weigh. Any ambient correction or conductor bundling takes a conductor rated exactly 50 amps below its breaker, and 4 AWG aluminum at 65 amps is the next size that restores headroom.

8 AWG or 6 AWG? It Depends on the Cable

This is where a 50 amp circuit differs from every smaller one, and it is worth being exact about, because both answers are right in their own context.

Conduit permits 8 AWG. Individual THHN or THWN-2 conductors in EMT, PVC or flexible conduit are read in the 75°C column set by the terminations, where 8 AWG copper is exactly 50 amps. Nothing about that is marginal in the legal sense; it is marginal in the practical sense, because the conductor has no headroom left for a correction factor.

NEC 240.4(D) does not decide this one. The small-conductor rule caps the overcurrent protection on 14, 12 and 10 AWG, and stops there. It does not reach 8 AWG, so it neither permits nor forbids anything at 50 amps. That is a real difference from a 40 amp circuit, where 240.4(D)(7) is what rules out 10 AWG and therefore creates the answer. At 50 amps the rule is silent and the wiring method does the work.

Search this question and you will find 6 AWG and 8 AWG given with equal confidence, usually with no condition attached. Both numbers are in the code. The disagreement is about which column the writer was reading.

Sites That Say 8 AWG

8 AWG is correct in conduit with 75°C terminations, where Table 310.16 rates it exactly 50 amps. A page that prints 8 AWG without naming the wiring method has quoted the 75°C column and left out the condition that makes it true. Follow it into an NM-B installation and the conductor is 40 amps behind a 50 amp breaker.

Sites That Say 6 AWG

6 AWG is correct everywhere, which is why it is the safer thing to publish without qualification. The cost is that it is one size larger than conduit installations require — more expensive, stiffer to pull and harder to terminate. A page that prints only 6 AWG is not wrong; it is conservative, and it is not telling you that you had a choice.

Sites That Quote the 90°C Column

8 AWG copper reads 55 amps at 90°C, and a page reading across that row will report it as comfortable. The 90°C column applies only where every termination in the circuit is listed 90°C, and residential breakers and lugs are listed 60/75°C. The 90°C figure is a derating starting point, not a circuit rating.

NEC Edition

Table 310.16 has changed between editions, and pages reproduced from older code books circulate without a date. The figures here follow NFPA 70-2023, and the 8 AWG and 6 AWG copper and aluminum rows were confirmed against multiple independent reproductions before publication. A chart with no edition on it cannot be checked against yours.

A 50 amp circuit in a house is a 240 volt circuit, and a 50 amp RV connection is a 120/240 volt circuit that is widely misread as 120 volts alone.

50 Amp at 240V

A 50 amp 240 volt circuit delivers 12 kW. It is fed by a two-pole breaker occupying two slots in the panel and picking up both busbars, so the two hot conductors are 240 volts apart. 50 amps is a standard overcurrent rating under NEC 240.6(A), and it is the size most large residential appliances land on once they outgrow a 40 amp circuit.

220V, 230V or 240V?

220 volts, 230 volts and 240 volts all describe the same residential circuit, and the wire size is the same for all three. The nominal supply in the United States is 120/240 volt single-phase, and that is the figure the NEC and Table 310.16 work from. The older designations — 110/220 and 115/230 — describe the same service under earlier nominal voltage standards, and they survive in conversation, on appliance nameplates and in search queries.

So 220v 50 amp wire size, 240v 50 amp wire size and wire size for 50 amps 240 volts all have one answer. Voltage sets how much power the circuit delivers and how much a given voltage drop costs as a percentage; current alone sets the conductor size, and the current is 50 amps in every case.

Three-Wire or Four-Wire?

Whether a 50 amp circuit needs three conductors or four is decided by whether the load uses 120 volts internally — the 6/3-versus-6/2 question in its practical form.

A load that is purely 240 volts — a welder, a 240-volt-only EV charger, an air handler — needs two hot conductors and an equipment grounding conductor. That is 6/2 cable: two insulated conductors plus a ground, with no neutral, because nothing in the equipment runs at 120 volts.

A load with 120 volt components — a range with a clock and an oven light, a spa pack with 120 volt controls, or anything fed through a sub-panel — needs a neutral as well. That is 6/3 cable: two hots, a neutral and a ground. An RV site is always four-wire, for reasons covered in its own section.

For new work the equipment grounding conductor is not optional. NEC 250.140 requires ranges, wall ovens, counter-mounted cooking units and clothes dryers on new branch circuits to be grounded through an equipment grounding conductor. The three-wire arrangement that bonded an appliance frame to the neutral is permitted only on existing branch circuits that have no EGC available, which is why the old 10-50 receptacle cannot be used for new work.

When You'd See 120V at 50 Amps

Almost never as a branch circuit, and the exception is the one that causes the confusion. A 50 amp 120 volt branch circuit is not a standard residential configuration — no common appliance draws 50 amps on a single hot leg when it could draw 25 on two.

The case people are usually thinking of is an RV. A 50 amp RV connection supplies 120 volts on each of two legs, so the coach's 120 volt circuits are fed at 120 volts while the whole connection is rated 50 amps per leg. That is not 50 amps at 120 volts; it is 12 kW, and the difference has its own section below.

50 amps sits above the 40 amp range and EV circuits and below the 60 amp subpanel and hot tub feeders. Three of the loads that land on it are governed by rules that produce a different conductor from the one the rest of this page implies, and each says so in its own section.

Electric Ranges and Ovens

A 50 amp circuit is the common choice for a full-size electric range, and it is usually more conductor than the calculation requires.

NEC Table 220.55, Column C, gives a single household range rated 8¾ to 12 kW a calculated demand of 8 kW, which is 33.3 amps at 240 volts. Note 1 to that table increases the Column C figure by 5 percent for each additional kilowatt above 12 kW, so a 15 kW range calculates to about 9.2 kW, or roughly 38 amps. The rating has to pass about 16 kW before the calculated demand exceeds 40 amps at all.

So a 50 amp range circuit is not required by the demand calculation for most ranges. Where 50 amps is genuinely the right size: a range whose own installation instructions call for it, a double oven, or a commercial-style unit. Where it is more than needed: a separately circuited cooktop or a single wall oven, which commonly want 30 or 40 amps and gain nothing from the larger conductor.

That is the reverse of the position one size down. At 40 amps the code names the amperage — NEC 210.19(C) sets 40 amperes as the minimum branch circuit for a range of 8¾ kW or more — and the honest answer is that most installers run 50 anyway. At 50 amps nothing in the code names the size, and the honest answer is that many circuits carrying it did not need it.

50 Amp Service and Feeders

A 50 amp service is a small one: an outbuilding, a workshop, a seasonal structure, or an older small dwelling that has never been upgraded.

The rule that governs it is the one that does not apply. NEC 310.12 permits the service and feeder conductors supplying the entire load of a one-family dwelling to be sized at 83 percent of the service rating — but only for a service or feeder rated 100 through 400 amperes. A 50 amp service is below that floor, so there is no reduction available. The conductors are sized directly from Table 310.16 at the full 50 amps, which means 6 AWG copper in cable or 8 AWG copper in conduit, exactly as a branch circuit would be.

This is worth stating plainly because the 83 percent allowance is the first thing people reach for on a service, and on a 100 amp service it genuinely applies. At 50 amps it does not.

50 Amp RV Sites

An RV site is not a dwelling service, and Article 551 governs it rather than the dwelling rules.

NEC 551.71 requires a 50 amp recreational vehicle site to be supplied by a 125/250 volt, 50 ampere receptacle of NEMA 14-50R configuration. That is four-wire: two hot conductors, a neutral and an equipment grounding conductor. The neutral and the equipment grounding conductor stay isolated from the service disconnect all the way through to the RV's own panel.

The conductor for the site supply follows the same Table 310.16 reading as any other 50 amp circuit; the park's overall service is calculated under Article 551's own provisions rather than the dwelling load rules.

Welders

A welder is the one load on this page whose conductor may legitimately be smaller than everything above implies, and the reason is duty cycle.

NEC 630.11 sizes the supply conductors for an arc welder to the nameplate rating. Where the nameplate does not state it, the conductor is sized to the rated primary current multiplied by the duty-cycle factor in Table 630.11(A) — 1.00 at 100 percent duty, 0.71 at 50 percent, 0.55 at 30 percent and 0.45 at 20 percent or less for a non-motor-generator welder.

Worked through: a welder with a 40 amp rated primary current at a 50 percent duty cycle needs a conductor rated 40 × 0.71 = 28.4 amps, even though its circuit may still be protected at 50 amps, because NEC 630.12 permits overcurrent protection for welders well above the conductor's ampacity.

This is the same body of rules producing a different answer, and it is anchored entirely to the equipment. The duty cycle and the rated primary current are printed on the welder. It is not general permission to undersize a 50 amp circuit: on a 50 amp range, spa, RV or sub-panel circuit the conductor is 6 AWG copper in cable or 8 AWG in conduit, exactly as the rest of this page states. Article 630 reaches welders and nothing else here.

EV Chargers, and Whether 10 AWG Is Acceptable

No — and the reason is the most useful thing on this page. A 50 amp breaker on 10 AWG copper is a code violation whatever the equipment actually draws.

The question comes up because a 32 amp charger on a 50 amp circuit draws well within what 10 AWG carries: 10 AWG copper is rated 35 amps at 75°C, comfortably above 32. But the breaker protects the conductor, not the load. Nothing stops a fault from putting 50 amps through that conductor, and NEC 240.4(D)(7) caps the overcurrent protection on 10 AWG copper at 30 amps regardless of temperature column or connected equipment.

The pairing to take away: what a conductor carries and what its overcurrent device permits are two different questions, and the smaller of the two answers governs.

There is also a sizing error hiding in the premise. Under NEC 625.42 electric vehicle charging is a continuous load, and NEC 625.41 requires the branch-circuit overcurrent protection to be rated at not less than 125 percent of the equipment's maximum load. A 32 amp charger is therefore a 40 amp circuit, not a 50 amp one — see 40 amp wire size. The charger that makes a 50 amp circuit is a 40 amp charger: 40 × 1.25 = 50.

Hot Tubs and Spas

50 amps is the standard size for a mid-to-large 240 volt hot tub, where at 40 amps it was the qualified case that suited only smaller single-pump units. The nameplate still decides, and some larger tubs run 60.

Two requirements apply regardless of the amperage:

• GFCI protection. NEC 680.44 requires the outlet supplying a self-contained spa or hot tub to be GFCI protected, which in practice means a two-pole GFCI breaker or a GFCI spa panel. A listed self-contained unit with integral GFCI protection for all its internal parts is the exception.
• A maintenance disconnect. NEC 680.13 requires it to be readily accessible, within sight of the equipment, and not less than 5 feet horizontally from the inside wall of the tub — far enough that nobody reaches it from the water. The distance is measured from the water's edge along the shortest path someone would take to reach it, and a permanently installed barrier that forces a 5 foot reach path satisfies the rule in place of the raw distance.

Most 240 volt spa packs include 120 volt controls, so the run is usually four-wire: 6/3 plus ground, or individual 6 AWG conductors in conduit.

Sub-Panels

A 50 amp feeder suits a detached garage, a workshop with hand tools, or a garden office. It is not enough for a shop running a table saw and a dust collector at once, where 60 to 100 amps is the honest starting point.

The feeder is 6 AWG copper in cable and always four-wire — two hots, a neutral and a separate equipment grounding conductor. Three rules govern the termination at the far end:

• The neutral bar and the ground bar in the sub-panel must be isolated from each other, and the main bonding jumper — the green screw or strap bonding the neutral bar to the enclosure — must be removed (NEC 408.40, 250.24).
• The neutral and the equipment ground are bonded at exactly one point in the system, the service disconnect, and a sub-panel is on the load side of it (NEC 250.32(B)).
• A sub-panel in a separate structure needs its own grounding electrode — a ground rod or rods — connected to its ground bar (NEC 250.32(A)), plus a disconnecting means at that structure (NEC 225.31).

A 50 amp receptacle comes in three configurations, and which one belongs on a circuit is decided by whether the load needs a neutral.

NEMA 14-50 — Four-Wire

The 14-50 carries two hots, a neutral and a ground. It is the configuration NEC 551.71 requires at a 50 amp RV site, and it is the one most commonly installed for ranges and for EV charging, because the neutral is there if the equipment needs 120 volts internally.

NEMA 6-50 — Three-Wire

The 6-50 carries two hots and a ground, with no neutral. It is current and correct for equipment that is purely 240 volts — welders and 240-volt-only EV charging equipment — and it costs less to run because the cable has one fewer conductor.

NEMA 10-50 — Legacy Only

The 10-50 carries two hots and a neutral with no separate equipment grounding conductor. NEC 250.140 requires an equipment grounding conductor on new range and dryer branch circuits, so the 10-50 is not permitted for new work. It survives on existing circuits, which is why it is still encountered.

What the Receptacle Rating Does and Does Not Decide

A 50 amp receptacle does not make a circuit a 50 amp circuit, and it does not size the conductor. The branch-circuit rating sizes the conductor; the receptacle has to be rated for the circuit it is installed on. Fitting a 50 amp receptacle to a circuit wired for less is one of the more common ways a dangerous circuit is created, because the receptacle then invites a load the conductor cannot carry.

GFCI protection is a separate question from the receptacle's configuration. Under NEC 210.8(A) in the 2023 code, receptacles rated 125 volts through 250 volts, supplied by single-phase branch circuits rated 150 volts or less to ground, require GFCI protection in the listed locations — which include garages, basements and outdoors, where most 50 amp receptacles are installed.

NM-B (Romex)

NM-B at 50 amps takes 6 AWG, and this is the rule that decides the page. The 60°C ceiling NEC 334.80 puts on non-metallic sheathed cable is what does it: 8 AWG copper reads 40 amps in that column and cannot carry 50; 6 AWG reads 55 and can.

This is exactly where the 60°C rule bites, and it is worth contrasting with one size down: at 40 amps, 8 AWG NM-B reads exactly 40 amps in the same column and is adequate with no margin. One step up to 50 amps and the same cable is no longer enough. That single step is why a 50 amp circuit in Romex costs noticeably more than a 40 amp one. Insulation types and temperature ratings are covered on the wire sizes explained page.

THHN in Conduit

Individual THHN or THWN-2 conductors in EMT, PVC or flexible conduit are the method that makes 8 AWG copper viable at 50 amps, because the circuit reads the 75°C column set by its terminations rather than the 60°C column set by a cable jacket.

The saving is real but thin. 8 AWG copper at exactly 50 amps has no headroom for an ambient correction or a fourth current-carrying conductor, so a conduit run through a hot attic or shared with another circuit lands back on 6 AWG. For a short, cool, dedicated run, 8 AWG in conduit is the economical and correct choice.

Direct Burial and UF-B

A 50 amp circuit crossing a yard — to a detached garage, a sub-panel or a hot tub — is either UF-B cable buried directly or individual conductors in buried conduit.

UF-B is held to the 60°C column exactly as NM-B is, so 6 AWG is the minimum for a buried cable at 50 amps. Burial depth is set by NEC Table 300.5 and depends on the wiring method and what covers it, which is a detail worth confirming against the table rather than assuming. Conduit is the more forgiving choice underground for a reason unrelated to ampacity: a buried conduit can be repulled when the circuit changes, and a direct-buried cable cannot.

What Size Ground Wire for a 50 Amp Circuit?

10 AWG copper, or 8 AWG aluminum, from NEC Table 250.122. The equipment grounding conductor is sized against the rating of the overcurrent device, not against the circuit conductors and not from the ampacity table.

Table 250.122 has no 50 ampere row — it steps from 40 amperes to 60 — so a 50 amp overcurrent device reads the next larger rating, the 60 ampere row, which calls for 10 AWG copper. The missing row is exactly the kind of thing that produces a confident wrong answer, so it is worth knowing the table does not list every breaker size.

One rule catches people on long runs. NEC 250.122(B) requires the equipment grounding conductor to be increased proportionally where the circuit conductors are upsized for voltage drop. Upsize 6 AWG to 4 AWG for a long feeder and the 10 AWG ground grows with it. Cable assemblies handle this themselves; individual conductors in conduit do not. The equipment grounding conductor sizes come from NEC Table 250.122, by overcurrent device rating rather than by conductor size: 14 AWG copper up to 20 amps, 12 AWG to 60, 10 AWG to 100, 8 AWG to 200.

Copper vs Aluminum for 50 Amps

Aluminum is a genuine option at 50 amps in a way it is not at smaller sizes. 6 AWG aluminum is rated exactly 50 amps at 75°C, 6 AWG is a size aluminum is readily available in, and a 50 amp feeder to an outbuilding is long enough for the cost and weight difference to matter.

Two things temper that. The conductor sits exactly on the table value, so it has no margin for any correction factor — 4 AWG aluminum at 65 amps is the size that restores it. And three requirements are not optional: every lug, breaker and device the conductor lands in must be listed for aluminum and marked AL/CU or AL9CU, the stripped conductor wants an antioxidant compound, and the termination needs a torque wrench set to the value marked on the equipment. An aluminum connection tightened by feel is the connection that runs hot.

Ampacity has no length column. A 50 amp circuit in 6 AWG copper is correct at any distance as far as Table 310.16 is concerned, and voltage drop is a separate limit the ampacity table says nothing about.

The mechanism is straightforward: the conductor's resistance is fixed per foot, so the voltage lost across the run grows with length while the ampacity stays where it is. At 50 amps the current is high enough that the loss accumulates faster than on a lighting circuit, and the industry target is 3 percent on a branch circuit — 7.2 volts out of 240.

Two things work in this circuit's favour. It is a 240 volt circuit, so a given voltage lost is half the percentage it would be at 120 volts. And many 50 amp loads are close to the panel — a range, a cooktop, a spa on the patio. The runs where drop decides the size are the outliers: a sub-panel at the end of a long yard, a detached garage, an RV pad at the property line.

When to Upsize to 4 AWG

Upsize when the run is long, when the load is continuous, or when both apply. A sub-panel feeder to a detached structure is the case that combines them.

Rather than publish a distance here, use the numbers for your own run in the calculator above: set the one-way distance and read the percentage. If the result exceeds 3 percent, the next step is 4 AWG copper — 85 amps at 75°C — and voltage drop by gauge and run length scales linearly with distance, so a circuit at 1.5 percent over 60 feet is at 3 percent over 120. Remember to increase the equipment grounding conductor with it, under NEC 250.122(B).

Using 8 AWG NM-B on a 50 Amp Breaker

The most common error at this amperage, and the one that looks correct. 8 AWG copper is 50 amps in the 75°C column, so the conductor appears to match the breaker — but inside NM-B cable NEC 334.80 holds it to 60°C and 40 amps. The same conductor is adequate in conduit and inadequate in cable, and the jacket is what decides.

Reading a 50 Amp RV Connection as 120 Volts

A 50 amp RV connection delivers 12 kW across two 120 volt legs, not 6 kW on one. Treating it as a 120 volt circuit leads to a three-wire installation where NEC 551.71 requires a four-wire 14-50, and to a supply sized for half the load the site can draw.

Putting 10 AWG on a 50 Amp Breaker for a Smaller Load

The load a circuit happens to carry does not size its conductor; the breaker does. 10 AWG behind a 50 amp device is a violation under NEC 240.4(D)(7) whatever is plugged into it.

Expecting the 83 Percent Allowance on a 50 Amp Service

NEC 310.12 applies to services and feeders rated 100 through 400 amperes. A 50 amp service is below the floor, so its conductors are sized at the full rating with no reduction.

Substituting Aluminum One Size for One Size

6 AWG aluminum is rated 50 amps and 6 AWG copper is rated 65. They are not interchangeable, and 8 AWG aluminum at 40 amps is not a 50 amp conductor at all. Aluminum also needs AL/CU-listed terminations and torqued connections.

Sizing a Welder Circuit From the Breaker

A welder's conductor is sized from its nameplate and duty cycle under NEC 630.11, which frequently permits a smaller conductor than the breaker suggests. Reading the breaker instead of the nameplate produces an oversized conductor at best, and a misunderstanding of Article 630 that gets applied to a non-welder circuit at worst.

The Nearest Sizes We Cover

If your load does not fit a 50 amp circuit, the nearest amperages covered here are 40 amp wire size at 40 amps and what size wire for a 100 amp breaker at 100 amps . Each works through the conductor, the cable type and the grounding conductor for that amperage in full.

Reference Pages

Every conductor size and temperature column sits in one place on the wire size chart, including the maximum breaker each size may be protected at. For the AWG system, insulation types and derating as subjects rather than as a single lookup, start at the wire sizes hub.