Wire Size Calculator

Mode:

Standard:

Inputs

System Type

Wire Material

Load Specification

Current (Amps)

Voltage

Distance (one-way, feet) Round-trip wire length: 50 ft

Target Voltage Drop

1% 3% 5% 10%

Cost Estimator (Optional)

Cost per foot ($/ft)

Results

Recommended: 6 AWG Passes

Copper wire for 48V system, 25ft one-way run

AWG	V Drop	Drop %	Status	Ampacity	Power Loss	Est. Cost
4 One size up	0.6V	1.3%	Passes	85A	24.6W	$125.00
6 Recommended	1.0V	2.0%	Passes	65A	39.3W	$87.50
8 One size down	1.6V	3.2%	Warning	50A	62.2W	$52.50

Actual Wire Sizes

Circles represent actual wire diameter. Place a ruler on your screen to verify. (Accuracy depends on your display's DPI settings)

4 0.271"

6 0.225"

8 0.188"

Understanding the Results

Voltage Drop: Energy lost as heat in the wire. Lower is better.
Ampacity: Maximum current the wire can safely carry continuously.
Power Loss: Watts wasted as heat. Larger wire = less loss.
Wire Size: Visual circles represent actual physical diameter at 96 CSS pixels per inch. For best accuracy, ensure browser zoom is at 100% and your OS display scaling matches your monitor's actual PPI.

Wire Size Reference Tables

Reference tables for wire sizing based on NEC (National Electrical Code) standards. These tables are provided for quick lookup when you already know your requirements.

Wire Ampacity (NEC Table 310.16)

Maximum current-carrying capacity at 75°C rated, 30°C ambient temperature. Values for 14-10 AWG reflect NEC 240.4(D) overcurrent protection limits.

AWG Size	Copper (A)	Aluminum (A)	Notes
4/0	230	180
3/0	200	155
2/0	175	135
1/0	150	120
1	130	100
2	115	90
3	100	75
4	85	65
6	65	50
8	50	40
10	30	25	NEC 240.4(D) limit; actual 310.16 ampacity is 35A (Cu), 30A (Al)
12	20	15	NEC 240.4(D) limit; actual 310.16 ampacity is 25A (Cu), 20A (Al)
14	15	—	NEC 240.4(D) limit; actual 310.16 ampacity is 20A
16	10	—	Limited power circuits; NEC 402.5 fixture wire ampacity
18	7	—	Limited power circuits; NEC 402.5 fixture wire ampacity
20	5	—	Low-voltage signal wire; not for general power wiring per NEC
22	3	—	Low-voltage signal wire; not for general power wiring per NEC

Source: NEC 2023 Table 310.16, with 240.4(D) limits applied for small gauges.

AWG Wire Diameter (ASTM B258)

Standard conductor diameters per American Wire Gauge. Overall diameters include typical THHN/THWN insulation.

AWG Size	Conductor Diameter	Overall Diameter
26	0.0159" (0.40 mm)	0.050" (1.27 mm)
25	0.0179" (0.45 mm)	0.053" (1.35 mm)
24	0.0201" (0.51 mm)	0.056" (1.42 mm)
23	0.0226" (0.57 mm)	0.059" (1.50 mm)
22	0.0254" (0.65 mm)	0.058" (1.47 mm)
21	0.0285" (0.72 mm)	0.067" (1.70 mm)
20	0.0320" (0.81 mm)	0.068" (1.73 mm)
19	0.0359" (0.91 mm)	0.076" (1.93 mm)
18	0.0403" (1.02 mm)	0.078" (1.98 mm)
17	0.0453" (1.15 mm)	0.087" (2.21 mm)
16	0.0508" (1.29 mm)	0.092" (2.34 mm)
15	0.0571" (1.45 mm)	0.101" (2.57 mm)
14	0.0641" (1.63 mm)	0.109" (2.77 mm)
13	0.0720" (1.83 mm)	0.119" (3.02 mm)
12	0.0808" (2.05 mm)	0.128" (3.25 mm)
11	0.0907" (2.30 mm)	0.136" (3.45 mm)
10	0.1019" (2.59 mm)	0.148" (3.76 mm)
9	0.1144" (2.91 mm)	0.173" (4.39 mm)
8	0.1285" (3.26 mm)	0.188" (4.78 mm)
7	0.1443" (3.67 mm)	0.209" (5.31 mm)
6	0.1620" (4.11 mm)	0.225" (5.71 mm)
5	0.1819" (4.62 mm)	0.247" (6.27 mm)
4	0.2043" (5.19 mm)	0.271" (6.88 mm)
3	0.2294" (5.83 mm)	0.296" (7.52 mm)
2	0.2576" (6.54 mm)	0.328" (8.33 mm)
1	0.2893" (7.35 mm)	0.360" (9.14 mm)
1/0	0.3249" (8.25 mm)	0.403" (10.24 mm)
2/0	0.3648" (9.27 mm)	0.443" (11.25 mm)
3/0	0.4096" (10.40 mm)	0.490" (12.45 mm)
4/0	0.4600" (11.68 mm)	0.543" (13.79 mm)

Source: ASTM B258 for conductor diameters. Overall diameters are approximate with typical THHN/THWN insulation.

Why does this table have more sizes?

This table includes all AWG sizes (including odd gauges like 5, 7, 9, 11, 13, 15 and small gauges 23-26) for reference purposes. However, odd gauge wires are rarely used for electrical power wiring. The NEC only specifies ampacity ratings for even-numbered gauges, which is why the Ampacity and Resistance tables above show fewer sizes. Odd gauges exist primarily for specialty applications like jewelry, electronics, and tensile/structural uses where current capacity isn't the primary concern.

Wire Resistance (NEC Chapter 9 Table 8)

DC resistance of stranded conductors at 75°C, in Ohms per 1000 feet. Used for voltage drop calculations.

AWG Size	Copper (Ω/kft)	Aluminum (Ω/kft)
4/0	0.0608	0.1
3/0	0.0766	0.126
2/0	0.0967	0.159
1/0	0.122	0.201
1	0.154	0.253
2	0.194	0.319
3	0.245	0.403
4	0.308	0.508
6	0.491	0.808
8	0.778	1.28
10	1.24	2.04
12	1.98	3.25
14	3.14	5.17
16	4.016
18	6.385
20	10.15
22	16.14

Source: NEC 2023 Chapter 9 Table 8, stranded conductors.

Voltage Drop Formula

The standard formula for calculating voltage drop in DC circuits and single-phase AC circuits.

V_drop = (2 × L × I × R) / 1000

Where:

V_drop = Voltage drop (volts)
L = One-way wire length (feet)
I = Current (amps)
R = Resistance (Ω per 1000 ft from table above)
2 = Factor for round-trip (positive and negative conductors)

Recommended maximum voltage drop:

3% for branch circuits (NEC recommendation)
5% total for feeder + branch combined
2-3% for solar/battery systems (efficiency)

Common Wire Size Applications

Typical residential and solar applications for each wire size (copper conductors).

AWG	Max Breaker	Common Applications
14	15A	Lighting circuits, general-purpose outlets
12	20A	Kitchen outlets, bathroom outlets, outdoor circuits
10	30A	Dryers, water heaters, small AC units
8	50A	Ranges, large AC units, EV chargers (Level 2)
6	65A	Subpanels, large appliances, hot tubs
4	85A	Subpanels, service entrance conductors
2	115A	100A subpanels, large solar inverters
1/0	150A	150A service entrance, battery bank connections
4/0	230A	200A service entrance, large battery systems

Note: Actual wire size requirements depend on circuit length, ambient temperature, and conduit fill. Always verify with local codes.