Wire Gauge Chart for 12V, 24V and 48V DC Systems (Ampacity + Voltage Drop)

A wire gauge chart for 12V, 24V and 48V systems needs two numbers for each copper size: ampacity, from NEC Table 310.16, and resistance per foot, from NEC Chapter 9 Table 8. Ampacity is how much current the wire can carry without overheating, and resistance sets your voltage drop. In low-voltage DC systems, voltage drop usually decides the size before ampacity does, so check both.

Electrical work can be dangerous: follow the manual, fuse and size every cable correctly, and use a licensed electrician for anything connected to household wiring.

Wire Gauge Chart: Ampacity and Resistance

AWG (copper)	Ampacity, 75°C column (NEC 310.16)	Resistance, Ω per 1,000ft (NEC Ch. 9 Table 8, stranded)
14	20A*	3.14
12	25A*	1.98
10	35A*	1.24
8	50A	0.778
6	65A	0.491
4	85A	0.308
2	115A	0.194
1/0	150A	0.122
2/0	175A	0.0967
4/0	230A	0.0608

\*NEC 240.4(D) limits overcurrent protection on 14, 12 and 10 AWG to 15A, 20A and 30A in most building wiring. The table assumes no more than three current-carrying conductors and 30°C ambient. Higher temperatures, bundling and conduit fill reduce ampacity. Insulation and terminal ratings also limit the column you can use.

Maximum One-Way Run for 3% Drop (Example Math)

Calculated from the resistance column: max one-way feet = (allowed drop V × 1,000) ÷ (2 × amps × Ω/1,000ft). Round-trip conductor, using the table’s 75°C resistance values. Real runs should add margin.

Load	12V (0.36V drop)	24V (0.72V)	48V (1.44V)
20A on 10 AWG	7.3ft	14.5ft	29ft
50A on 6 AWG	7.3ft	14.7ft	29ft
100A on 2/0	18.6ft	37ft	74ft
150A on 4/0	19.7ft	39ft	79ft

Each step up in system voltage doubles the run you can make with the same wire at the same current. Since doubling the voltage also halves the current for the same power, the real gain is even bigger.

How to Use the Chart

1. Find the current: watts ÷ volts. For an inverter, use its maximum DC input current from the datasheet.
2. Pick the smallest gauge whose ampacity covers the current, plus any code multipliers (125% for continuous loads).
3. Check voltage drop over the round-trip length, and size up if needed.
4. Fuse the wire close to the battery, rated at or below the wire’s ampacity.

Marine and Vehicle Wiring

Boats follow ABYC E-11 tables, and vehicles often use SAE wire. Both differ from NEC building wire. Use the standard that applies to your installation and the equipment maker’s manual.

Worked Example: Sizing a 24V Inverter Cable

Illustrative inputs: a 2,000W inverter on a 24V battery, 8ft one-way (16ft round trip), target drop of 3% or less.

Step	Math	Result
DC current (assume 90% efficiency)	2,000 ÷ 0.9 ÷ 24	about 93A
Allowed drop at 3%	24 × 0.03	0.72V
Max resistance	0.72 ÷ 93	0.0077Ω
Per 1,000ft (16ft run)	0.0077 ÷ 16 × 1,000	0.48Ω per 1,000ft
Smallest size at or below that	NEC Ch. 9 Table 8	6 AWG (0.491Ω) is just over; 4 AWG (0.308Ω) fits

Now check ampacity: 4 AWG copper with 90°C insulation is rated 95A in NEC Table 310.16, and 93A × 1.25 for continuous use is about 116A, so many installers step up to 2 AWG for margin. Always follow the inverter manual’s minimum cable size. The same inverter on 12V would draw about 185A, which is why 12V vs 24V vs 48V matters.

Same Load, Three Voltages

2,000W inverter	DC amps	Typical cable for 8ft, 3% drop
12V	about 185A	2/0 to 4/0 AWG
24V	about 93A	4 to 2 AWG
48V	about 46A	8 to 6 AWG

Calculated from Table 8 resistances; confirm with your equipment manual.

Step-by-Step Sizing Checklist

1. Find the maximum current (inverter watts ÷ efficiency ÷ battery voltage).
2. Multiply by 1.25 for continuous loads.
3. Pick a size whose ampacity covers that.
4. Run the voltage drop math with the voltage drop calculation.
5. Use the larger of the two sizes.
6. Fuse the cable at or below its ampacity; see what size fuse do I need.
7. Crimp lugs properly; see how to crimp battery cable.

Fine-Strand vs Building Wire

Battery cable and welding cable use many fine strands for flexibility. Some lugs and terminals are only listed for standard Class B stranding, so match lugs to the cable class. Fine-strand cable needs lugs and crimpers made for it.

FAQ

What wire size do I need for 100 amps at 12V?

For ampacity alone, 2 AWG covers 115A in the 75°C column, but voltage drop often calls for 1/0 or larger on longer runs.

Is welding cable OK for batteries?

It’s flexible and widely used in mobile systems, but it may not be listed for building wiring. Check the code that applies to you.

Copper or aluminum?

This chart is for copper. Aluminum needs larger sizes and rated terminals.

Does a 48V system really save on copper?

Yes. Current is a quarter of a 12V system for the same watts, so cables can be several sizes smaller.

What insulation rating should battery cable have?

Look for a 90°C or 105°C rating, and use the ampacity column that matches your terminals’ temperature rating.

Sources: NFPA 70 (NEC) 2023: Table 310.16, Chapter 9 Table 8, 240.4(D); ABYC E-11 (marine); NFPA 70 (NEC) Table 310.16. Accessed Oct 2026.

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