What size wire do I need for a 200 amp breaker?

4/0 AWG copper is the smallest conductor our model estimates at or above 200 A using a 75 °C insulation rating; 250 kcmil is required if the terminations are limited to 60 °C. In aluminium the equivalent is 250 kcmil. Verify against the code edition adopted locally before installing.

Can I use aluminium wire on a 200 amp circuit?

Yes, where the terminations are rated for aluminium. Because aluminium carries roughly 78% of the current of the same copper size, a 200 A circuit steps up to 250 kcmil and uses K = 21.2 in the voltage-drop formula instead of 12.9.

How far can a 200 amp circuit run?

On 4/0 AWG copper the 3% voltage-drop guideline is reached near 147 ft one-way at 120 V and 295 ft at 240 V. Longer runs need the next size or two up — length, not ampacity, decides most feeder sizes.

Is a 200 amp breaker sized at 100% of the load?

Only for non-continuous loads. A continuous load is designed at 125%, so 200 A of continuous current becomes 250 A of design current and lands on a 250 A device with conductors sized to match.

What is typically on a 200 amp circuit?

Commonly standard residential service entrance. The load type also drives the receptacle and disconnect ratings, not just the conductor size.

What Size Wire for a 200 Amp Breaker?

Conductor size, aluminium equivalent, derating and maximum run length for a 200 amp circuit — all derived from published conductor geometry and the voltage-drop formula.

Quick answer

A 200 amp circuit needs 4/0 AWG copper with 75 °C terminations, or 250 kcmil aluminium. 250 kcmil copper applies where equipment terminals are limited to 60 °C. Voltage drop reaches 3% at roughly 295 ft one-way on 240 V and 147 ft on 120 V.

Formula estimate

Copper @ 75 °C

4/0 AWG

Copper @ 60 °C

250 kcmil

Aluminium @ 75 °C

250 kcmil

3% drop @ 240 V

295ft

Conductor options for 200 A

Estimated ampacity of each candidate size, so you can see the margin you are buying.

Material / rating	Minimum size	Estimated ampacity	Margin over 200 A
Copper, 60 °C	250 kcmil	217 A	+17 A
Copper, 75 °C	4/0 AWG	230 A	+30 A
Copper, 90 °C	3/0 AWG	223 A	+23 A
Aluminium, 75 °C	250 kcmil	200 A	+0 A
Aluminium, 90 °C	4/0 AWG	202 A	+2 A

Ampacity estimated as I = 0.0670 × cmil^0.6505, scaled for insulation rating and material.

Source & method: Conductor areas come from the ASTM B258 relationship d = 5 × 92^((36 − n) / 39). Ampacity is a fitted physical model, not a reproduction of any code table, and runs within roughly ±8% of published values.

Maximum run length on 4/0 AWG copper

One-way distance before voltage drop passes the 3% and 5% guidelines.

System	3% limit	5% limit	Drop @ 100 ft
120 V 1Ø	147 ft	246 ft	2.03%
240 V 1Ø	295 ft	492 ft	1.02%
208 V 3Ø	295 ft	492 ft	1.02%
480 V 3Ø	681 ft	1,136 ft	0.44%

Source & method: VD = 2 × K × I × L / cmil single phase, 1.732 × K × I × L / cmil three phase, with K = 12.9 for copper. 4/0 AWG is 211,600 circular mils and 0.0490 Ω per 1000 ft at 20 °C.

Wire size by run length for 200 A

Ampacity sets the floor; distance is what actually forces the upsize on long runs. Smallest copper conductor that carries the load and still holds 3% drop.

One-way run	120 V 1Ø	240 V 1Ø	480 V 3Ø
50 ft	4/0 AWG	4/0 AWG	4/0 AWG
75 ft	4/0 AWG	4/0 AWG	4/0 AWG
100 ft	4/0 AWG	4/0 AWG	4/0 AWG
150 ft	250 kcmil	4/0 AWG	4/0 AWG
200 ft	300 kcmil	4/0 AWG	4/0 AWG
250 ft	400 kcmil	4/0 AWG	4/0 AWG
300 ft	500 kcmil	250 kcmil	4/0 AWG

Sized on both criteria at once: estimated 75 C ampacity and 3% voltage drop at the stated one-way distance.

Source & method: A dash means no listed size holds 3% at that distance and voltage — split the load, raise the system voltage, or move the panel closer.

Hot attics, conduit runs and bundling

What a 200 A circuit actually needs once ambient temperature and conductor count are applied.

Ambient	3 conductors	4–6 conductors	7–9 conductors
30 °C	4/0 AWG	250 kcmil	300 kcmil
40 °C	4/0 AWG	300 kcmil	400 kcmil
50 °C	300 kcmil	400 kcmil	500 kcmil
60 °C	400 kcmil	600 kcmil	750 kcmil

Source & method: Ambient correction F = √((Tc − Ta) / (Tc − 30)) with Tc = 75 °C; bundling adjustment uses the standard stepped schedule (1.00 / 0.80 / 0.70). The conductor shown is the smallest copper size whose corrected ampacity still carries 200 A.

Where 200 A circuits are actually used

200 A is the standard modern residential service size and a common commercial subfeeder. At this rating you are almost never wiring a load — you are wiring a service entrance or a panel feeder, and the conductor is sized against the calculated service load rather than a single appliance nameplate.

Service and feeder conductors get treatment that branch circuits do not. A dwelling service or main-power feeder is permitted to be sized at 83% of the service rating, which is why 4/0 aluminium is routine on a 200 A residential service even though 200 A of ordinary feeder would call for more copper. That allowance applies to the main service or feeder only, not to the branch circuits downstream.

The practical constraints at 200 A are mechanical and thermal rather than electrical: lug size and termination temperature at the panel, conduit fill and pulling tension on parallel sets, and the 75 °C termination limit that caps what the 90 °C insulation on the conductor would otherwise allow. Voltage drop matters on long rural service laterals, where a 300 ft run can force the next size up on drop alone.

Continuous loads

A continuous load — one expected to run three hours or more, like commercial lighting or an EV charger — is designed at 125% of the load current. 200 A continuous becomes 250 A of design current, which lands on a 250 A overcurrent device and 250 kcmil copper.

Frequently asked

What size wire do I need for a 200 amp breaker?: 4/0 AWG copper is the smallest conductor our model estimates at or above 200 A using a 75 °C insulation rating; 250 kcmil is required if the terminations are limited to 60 °C. In aluminium the equivalent is 250 kcmil. Verify against the code edition adopted locally before installing.
Can I use aluminium wire on a 200 amp circuit?: Yes, where the terminations are rated for aluminium. Because aluminium carries roughly 78% of the current of the same copper size, a 200 A circuit steps up to 250 kcmil and uses K = 21.2 in the voltage-drop formula instead of 12.9.
How far can a 200 amp circuit run?: On 4/0 AWG copper the 3% voltage-drop guideline is reached near 147 ft one-way at 120 V and 295 ft at 240 V. Longer runs need the next size or two up — length, not ampacity, decides most feeder sizes.
Is a 200 amp breaker sized at 100% of the load?: Only for non-continuous loads. A continuous load is designed at 125%, so 200 A of continuous current becomes 250 A of design current and lands on a 250 A device with conductors sized to match.
What is typically on a 200 amp circuit?: Commonly standard residential service entrance. The load type also drives the receptacle and disconnect ratings, not just the conductor size.