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.

30A

Ampacity

at 60°C

2.07%

Voltage drop

2.49V

117.5V

At load

receiving end

10,380

Circular mils

5.26 mm²

Min for ampacity

12 AWG

6,530 CM

Min for ≤3% VD ← governs

10 AWG

10,380 CM

20A

Breaker size

NEC 240.6(A)

~$72

Wire cost est.

100 ft THHN

3/4" EMT

Conduit size

3 conductors

12 AWG Cu

Ground wire (EGC)

NEC 250.122

48W

Power loss

~$58.87/yr

⚠Long run (50 ft) governs — upsized from 12 AWG to 10 AWG for ≤3% VD.

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).

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
Al ampacity (75°C)	30A	40A
VD at 20A / 50ft	2.49V (2.07%)	1.56V (1.3%)
Resistance (Cu/kft)	1.24Ω	0.778Ω
Common insulations	NM-B, THHN, THWN, UF-B	THHN, THWN, USE-2, XHHW

Ampacity comparison

Visual Analysis1 series4 points

Interactive bar view for 1 series and 4 sampled points, built for quick reading and clear comparison.

Trend

Upward

Min

Max

Insight

Ampacity comparison shows an upward pattern, with a visible peak around 8 AWG 75°C at 50.

X-axis: Wire gauge + temp ratingY-axis: Ampacity (A)

Ampacity comparison

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.

How to choose between these gauges

10 AWG is the smaller conductor when its circular-mil area is lower; 8 AWG is larger when its circular-mil area is higher. The larger conductor generally lowers voltage drop and heat but costs more and may require larger raceway.

For the modeled 20A, 50 ft, 120V example, compare both ampacity and voltage drop rather than choosing by ampacity alone.

Use the smaller listed gauge only when it passes ampacity, voltage drop, termination temperature, and installation-condition checks for the real circuit.

Safety notes for replacing wire sizes

Do not downsize an existing circuit from a comparison table. Breaker size, conductor material, insulation, raceway fill, equipment label, and local code decide the legal minimum.

A larger wire can still be wrong if terminals are not rated for the conductor material or size, or if the equipment nameplate requires a specific branch-circuit treatment.

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.

30A

Ampacity

at 60°C

2.07%

Voltage drop

2.49V

117.5V

At load

receiving end

10,380

Circular mils

5.26 mm²

Min for ampacity

12 AWG

6,530 CM

Min for ≤3% VD ← governs

10 AWG

10,380 CM

20A

Breaker size

NEC 240.6(A)

~$72

Wire cost est.

100 ft THHN

3/4" EMT

Conduit size

3 conductors

12 AWG Cu

Ground wire (EGC)

NEC 250.122

48W

Power loss

~$58.87/yr

⚠Long run (50 ft) governs — upsized from 12 AWG to 10 AWG for ≤3% VD.

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).

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
Al ampacity (75°C)	30A	40A
VD at 20A / 50ft	2.49V (2.07%)	1.56V (1.3%)
Resistance (Cu/kft)	1.24Ω	0.778Ω
Common insulations	NM-B, THHN, THWN, UF-B	THHN, THWN, USE-2, XHHW

Ampacity comparison

Visual Analysis1 series4 points

Interactive bar view for 1 series and 4 sampled points, built for quick reading and clear comparison.

Trend

Upward

Min

Max

Insight

Ampacity comparison shows an upward pattern, with a visible peak around 8 AWG 75°C at 50.

X-axis: Wire gauge + temp ratingY-axis: Ampacity (A)

Ampacity comparison

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.

How to choose between these gauges

For the modeled 20A, 50 ft, 120V example, compare both ampacity and voltage drop rather than choosing by ampacity alone.

Use the smaller listed gauge only when it passes ampacity, voltage drop, termination temperature, and installation-condition checks for the real circuit.

Safety notes for replacing wire sizes

Do not downsize an existing circuit from a comparison table. Breaker size, conductor material, insulation, raceway fill, equipment label, and local code decide the legal minimum.

A larger wire can still be wrong if terminals are not rated for the conductor material or size, or if the equipment nameplate requires a specific branch-circuit treatment.