10 AWG vs 8 AWG — Wire Gauge Comparison

Compare 10 AWG (35A @ 75°C, 10,380 CM) vs 8 AWG (50A @ 75°C, 16,510 CM). Includes copper/aluminum assumptions, ampacity, voltage-drop planning, and NEC/local-code safety notes.

Load current (amps)

One-way distance (ft)

System voltage

Conductor

Insulation temp

Max VD% (NEC rec 3%)

Phase

Advanced options — derating, breaker & conduit

Conductors in raceway

Ambient temperature

Continuous load (3+ hrs)Breaker ≥ 125% per NEC 210.19

10 AWGcopper

Ampacity OKVD 2.07%VD GOVERNS

Long run (50 ft) requires upsizing from 12 AWG to 10 AWG for voltage drop.

Ampacity30Aat 60°C

Voltage drop2.07%2.49V

At load117.5Vreceiving end

Circular mils10,3805.26 mm²

Min for ampacity

12 AWG

6,530 CM

Min for ≤3% VDgoverns

10 AWG

10,380 CM

Breaker size20ANEC 240.6(A)

Wire cost est.~$72100 ft THHN

Conduit size3/4" EMT3 conductors

Ground (EGC)12 AWG CuNEC 250.122

Power loss48W~$58.87/yr

Copper vs Aluminum (for 20A at 50 ft on 120V)

Copper

12 AWG

VD: 3.3% · 3.31 mm²

Aluminum

10 AWG

VD: 3.4% · 5.26 mm²

10 AWG

35A @ 75°C · 5.26 mm² · 10,380 CM

Used for 30A circuits — dryers, water heaters, small AC units.

8 AWG

50A @ 75°C · 8.37 mm² · 16,510 CM

40–50A circuits — EV chargers (Level 2), large AC units, cooking ranges (smaller).

Verify this result

This answer is computed by WireGaugeRegistry.compare (v1.0.0), current for the NEC 2023 edition. The same inputs always produce the same figure and the same fingerprint below, so you can reproduce and cite it.

Standards

NEC 2023 — Table 310.16 (allowable ampacities)
ASTM B258-18 — AWG diameters and cross-sectional areas

Assumptions

Ampacity columncopper, 75°C insulation
Conditions≤3 current-carrying conductors, 30°C ambient
Resistance basisDC, ohms per 1,000 ft at 75°C (NEC Ch.9 Table 8)

Inputs & outputs

in · wireA10awg
in · wireB8awg
in · ampacityCu75A35
in · ampacityCu75B50
in · areaMm2A5.26
in · areaMm2B8.37
in · resistanceCuPerKftA1.24
in · resistanceCuPerKftB0.778
out · ampacityDeltaA-15
out · higherAmpacity8 AWG
out · areaRatio0.6284
out · resistanceRatio1.5938

Computation fingerprint (SHA-256)

16d722e7b9bb39c2048860a2632d659838e04d7dac7949eec3ec64af2dd9c891

10 AWG vs 8 AWG — Wire Gauge Comparison

10 AWG and 8 AWG copper sit on opposite sides of a line the NEC draws explicitly: the small-conductor rule. 16 directly, at 40 A on the 60 °C column or 50 A at 75 °C. That single rule sorts most residential loads between them: 30 A circuits — dryers, standard water heaters, many mini-splits — are 10 AWG territory, while 40–50 A circuits — ranges, larger heat pumps, EV charging — start at 8 AWG.

10 AWG vs 8 AWG: Which is right for your project?

10 AWG has 35A ampacity and 10,380 circular mils. 8 AWG has 50A ampacity and 16,510 circular mils.

For 20A at 50 ft on 120V: 10 AWG drops 2.07% vs 8 AWG drops 1.3%.

Head-to-head comparison

Source: NEC 2023 Table 310.16. Voltage drop formula: VD = (2 × K × I × L) / CM.

Specification	10 AWG	8 AWG
AWG	10 AWG	8 AWG
Diameter	0.1019" / 2.588mm	0.1285" / 3.264mm
Area	5.26 mm²	8.37 mm²
Circular mils	10,380	16,510
Cu ampacity (60°C)	30A	40A
Cu ampacity (75°C)	35A	50A

Showing 6 of 10 rows for Specification.

Which gauge wins for this setup?

10 AWG vs 8 AWG must be decided by ampacity, voltage drop, material, terminals, and raceway constraints together.

Voltage drop across common loads

Voltage-drop comparison at 50 ft on 120V. Ampacity still must be checked separately for each load.

Load	10 AWG VD	8 AWG VD	Planning signal
15A	1.55%	0.98%	Both pass
20A	2.07%	1.3%	Both pass
30A	3.11%	1.95%	8 AWG preferred
40A	4.14%	2.6%	8 AWG preferred
50A	5.18%	3.26%	Upsize/check distance
60A	6.21%	3.91%	Upsize/check distance

Practical impact of choosing the larger gauge

Upsizing can reduce voltage drop and heat, but may raise cost, raceway size, and termination constraints.

Decision factor	10 AWG	8 AWG	Difference
Circular mils	10,380	16,510	6,130 CM
Area	5.26 mm2	8.37 mm2	3.11 mm2
Ampacity	35A	50A	15A
Resistance	1.24 ohm/kft	0.778 ohm/kft	Lower resistance means lower voltage drop.
VD at 20A/50ft	2.07%	1.3%	0.77 percentage points

Copper and aluminum ampacity comparison

Temperature-rating and material rules can change the final legal choice even when AWG size looks similar.

Material / rating	10 AWG	8 AWG	Selection note
Copper 60C	30A	40A	Common small-branch-circuit terminal basis.
Copper 75C	35A	50A	Often relevant for larger listed terminals.
Copper 90C	40A	55A	Usually used for adjustment/correction, not final terminal ampacity.
Aluminum 75C	30A	40A	Only where aluminum conductors and terminations are listed.
Resistance	1.24 ohm/kft	0.778 ohm/kft	Lower resistance reduces voltage drop.

Wire gauge comparison FAQ

Is 8 AWG always better than 10 AWG?
The larger conductor usually lowers resistance and voltage drop, but cost, raceway fill, and terminal compatibility still matter.

Which gauge has less voltage drop?
8 AWG has the lower modeled voltage drop for 20A at 50 ft.

Can one gauge replace the other?
Only when the replacement satisfies breaker, ampacity, voltage drop, terminal, equipment-label, insulation, and local-code requirements.

Which temperature rating should be used?
This comparison uses 75C for the modeled ampacity. Real terminals and equipment labels decide whether 60C, 75C, or 90C values apply.

Common mistakes with 10 AWG vs 8 AWG

Putting 10 AWG on a 35 A breaker because Table 310.16 shows 35 A at 75 °C. NEC 240.4(D)(7) forbids it for ordinary circuits: 30 A is the maximum overcurrent protection for 10 AWG copper. The 35 A figure only becomes usable under specific equipment rules such as motor or HVAC circuits sized per nameplate under 240.4(G).

Counting 8 AWG NM-B as a 50 A conductor. NM-B is restricted to the 60 °C column by NEC 334.80, and 8 AWG at 60 °C is 40 A. The 50 A rating requires 75 °C wiring methods — THHN/THWN-2 in conduit, SE cable where permitted — plus 75 °C-rated terminations per 110.14(C).

10 AWG vs 8 AWG — frequently asked questions

When is 10 AWG genuinely enough?
For any circuit whose overcurrent device is 30 A or less and whose run is short enough to hold voltage drop: electric dryers (30 A), most 4,500 W water heaters, and single-zone mini-splits with 25–30 A maximum overcurrent ratings. At 1.24 Ω per 1,000 ft, a 30 A load stays inside a 3 % drop on 240 V out to roughly 96 ft one-way.

Is it wrong to run 8 AWG where 10 AWG would do?
No — upsizing is always permitted and sometimes wise on long runs or where a future load upgrade is plausible. The costs are real, though: on this page's pricing basis 8 AWG copper runs roughly 60 % more per foot than 10 AWG, it needs larger-volume boxes and conduit fill, and the terminating device must be listed for the larger conductor.

Do the same breaker caps apply to aluminum?
The small-conductor rule has aluminum entries too: NEC 240.4(D) caps 10 AWG aluminum at 25 A. In practice aluminum enters this size class one gauge up — 8 AWG aluminum (30 A at 60 °C, 40 A at 75 °C) plays the role 10 AWG copper plays, which is why like-for-like aluminum swaps always shift at least one size.

Sources & Standards

National Fire Protection Association. "NFPA 70: National Electrical Code," Table 310.16, 2023 Edition.Allowable ampacities of insulated copper and aluminum conductors (60°C / 75°C / 90°C columns) used in wire sizing
ASTM International. "Standard Specification for Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors." ASTM B258-18, 2018.AWG conductor diameters and cross-sectional areas used in gauge conversions

10 AWG vs 8 AWG — Wire Gauge Comparison

Compare 10 AWG (35A @ 75°C, 10,380 CM) vs 8 AWG (50A @ 75°C, 16,510 CM). Includes copper/aluminum assumptions, ampacity, voltage-drop planning, and NEC/local-code safety notes.

Load current (amps)

One-way distance (ft)

System voltage

Conductor

Insulation temp

Max VD% (NEC rec 3%)

Phase

Advanced options — derating, breaker & conduit

Conductors in raceway

Ambient temperature

Continuous load (3+ hrs)Breaker ≥ 125% per NEC 210.19

10 AWGcopper

Ampacity OKVD 2.07%VD GOVERNS

Long run (50 ft) requires upsizing from 12 AWG to 10 AWG for voltage drop.

Ampacity30Aat 60°C

Voltage drop2.07%2.49V

At load117.5Vreceiving end

Circular mils10,3805.26 mm²

Min for ampacity

12 AWG

6,530 CM

Min for ≤3% VDgoverns

10 AWG

10,380 CM

Breaker size20ANEC 240.6(A)

Wire cost est.~$72100 ft THHN

Conduit size3/4" EMT3 conductors

Ground (EGC)12 AWG CuNEC 250.122

Power loss48W~$58.87/yr

Copper vs Aluminum (for 20A at 50 ft on 120V)

Copper

12 AWG

VD: 3.3% · 3.31 mm²

Aluminum

10 AWG

VD: 3.4% · 5.26 mm²

10 AWG

35A @ 75°C · 5.26 mm² · 10,380 CM

Used for 30A circuits — dryers, water heaters, small AC units.

8 AWG

50A @ 75°C · 8.37 mm² · 16,510 CM

40–50A circuits — EV chargers (Level 2), large AC units, cooking ranges (smaller).

Verify this result

Standards

NEC 2023 — Table 310.16 (allowable ampacities)
ASTM B258-18 — AWG diameters and cross-sectional areas

Assumptions

Ampacity columncopper, 75°C insulation
Conditions≤3 current-carrying conductors, 30°C ambient
Resistance basisDC, ohms per 1,000 ft at 75°C (NEC Ch.9 Table 8)

Inputs & outputs

in · wireA10awg
in · wireB8awg
in · ampacityCu75A35
in · ampacityCu75B50
in · areaMm2A5.26
in · areaMm2B8.37
in · resistanceCuPerKftA1.24
in · resistanceCuPerKftB0.778
out · ampacityDeltaA-15
out · higherAmpacity8 AWG
out · areaRatio0.6284
out · resistanceRatio1.5938

Computation fingerprint (SHA-256)

16d722e7b9bb39c2048860a2632d659838e04d7dac7949eec3ec64af2dd9c891

10 AWG vs 8 AWG — Wire Gauge Comparison

10 AWG vs 8 AWG: Which is right for your project?

10 AWG has 35A ampacity and 10,380 circular mils. 8 AWG has 50A ampacity and 16,510 circular mils.

For 20A at 50 ft on 120V: 10 AWG drops 2.07% vs 8 AWG drops 1.3%.

Head-to-head comparison

Source: NEC 2023 Table 310.16. Voltage drop formula: VD = (2 × K × I × L) / CM.

Specification	10 AWG	8 AWG
AWG	10 AWG	8 AWG
Diameter	0.1019" / 2.588mm	0.1285" / 3.264mm
Area	5.26 mm²	8.37 mm²
Circular mils	10,380	16,510
Cu ampacity (60°C)	30A	40A
Cu ampacity (75°C)	35A	50A

Showing 6 of 10 rows for Specification.

Which gauge wins for this setup?

10 AWG vs 8 AWG must be decided by ampacity, voltage drop, material, terminals, and raceway constraints together.

Voltage drop across common loads

Voltage-drop comparison at 50 ft on 120V. Ampacity still must be checked separately for each load.

Load	10 AWG VD	8 AWG VD	Planning signal
15A	1.55%	0.98%	Both pass
20A	2.07%	1.3%	Both pass
30A	3.11%	1.95%	8 AWG preferred
40A	4.14%	2.6%	8 AWG preferred
50A	5.18%	3.26%	Upsize/check distance
60A	6.21%	3.91%	Upsize/check distance

Practical impact of choosing the larger gauge

Upsizing can reduce voltage drop and heat, but may raise cost, raceway size, and termination constraints.

Decision factor	10 AWG	8 AWG	Difference
Circular mils	10,380	16,510	6,130 CM
Area	5.26 mm2	8.37 mm2	3.11 mm2
Ampacity	35A	50A	15A
Resistance	1.24 ohm/kft	0.778 ohm/kft	Lower resistance means lower voltage drop.
VD at 20A/50ft	2.07%	1.3%	0.77 percentage points

Copper and aluminum ampacity comparison

Temperature-rating and material rules can change the final legal choice even when AWG size looks similar.

Material / rating	10 AWG	8 AWG	Selection note
Copper 60C	30A	40A	Common small-branch-circuit terminal basis.
Copper 75C	35A	50A	Often relevant for larger listed terminals.
Copper 90C	40A	55A	Usually used for adjustment/correction, not final terminal ampacity.
Aluminum 75C	30A	40A	Only where aluminum conductors and terminations are listed.
Resistance	1.24 ohm/kft	0.778 ohm/kft	Lower resistance reduces voltage drop.

Wire gauge comparison FAQ

Is 8 AWG always better than 10 AWG?
The larger conductor usually lowers resistance and voltage drop, but cost, raceway fill, and terminal compatibility still matter.

Which gauge has less voltage drop?
8 AWG has the lower modeled voltage drop for 20A at 50 ft.

Can one gauge replace the other?
Only when the replacement satisfies breaker, ampacity, voltage drop, terminal, equipment-label, insulation, and local-code requirements.

Which temperature rating should be used?
This comparison uses 75C for the modeled ampacity. Real terminals and equipment labels decide whether 60C, 75C, or 90C values apply.

Common mistakes with 10 AWG vs 8 AWG

10 AWG vs 8 AWG — frequently asked questions

Sources & Standards

National Fire Protection Association. "NFPA 70: National Electrical Code," Table 310.16, 2023 Edition.Allowable ampacities of insulated copper and aluminum conductors (60°C / 75°C / 90°C columns) used in wire sizing
ASTM International. "Standard Specification for Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors." ASTM B258-18, 2018.AWG conductor diameters and cross-sectional areas used in gauge conversions