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Good question — the ampacity (current-carrying capacity) of a wire depends on:

Wire gauge (AWG size)
Insulation type and temperature rating (e.g. THHN, NM-B, etc.)
Ambient temperature
Whether the wire is in free air or inside conduit/bundled

Here’s a general reference table for copper wires (the most common), based on the NEC (National Electrical Code) ampacity for 60°C / 75°C / 90°C insulation ratings:

AWG Size	Ampacity @60°C	Ampacity @75°C	Ampacity @90°C	Common Circuit Use
18 AWG	6 A	7 A	7 A	Low-voltage control, LED lights
16 AWG	8 A	10 A	13 A	Extension cords (light-duty)
14 AWG	15 A	20 A	25 A	15A household circuits (standard)
12 AWG	20 A	25 A	30 A	20A household circuits
10 AWG	30 A	35 A	40 A	Water heaters, dryers
8 AWG	40 A	50 A	55 A	Electric ranges, subpanels
6 AWG	55 A	65 A	75 A	Main feeds, EV chargers
4 AWG	70 A	85 A	95 A	Large appliances, feeders
2 AWG	95 A	115 A	130 A	Subpanel feeders
1 AWG	110 A	130 A	145 A	Main feeders
1/0 AWG	125 A	150 A	170 A	Main service or subpanel feeders
2/0 AWG	145 A	175 A	195 A	Service feeders
3/0 AWG	165 A	200 A	225 A	Service feeders
4/0 AWG	195 A	230 A	260 A	Service feeders

🔹 Typical rule of thumb (house wiring, NM-B cable):

14 AWG → 15 amps max
12 AWG → 20 amps max
10 AWG → 30 amps max

Those values follow NEC 240.4(D), which limits branch circuit sizes for safety.

Here’s the same table for aluminum wire (common in large-gauge feeder and service cables):

AWG Size (Aluminum)	Ampacity @60°C	Ampacity @75°C	Ampacity @90°C	Typical Use
12 AWG	15 A	20 A	25 A	Lighting, small branch circuits
10 AWG	25 A	30 A	35 A	Light appliances
8 AWG	35 A	40 A	45 A	Small subpanels
6 AWG	40 A	50 A	55 A	Feeders, small EV chargers
4 AWG	55 A	65 A	75 A	Feeders
2 AWG	75 A	90 A	100 A	Subpanel or service feeders
1 AWG	85 A	100 A	115 A	Subpanel feeders
1/0 AWG	100 A	120 A	135 A	Service entrance
2/0 AWG	115 A	135 A	150 A	Service entrance
3/0 AWG	130 A	155 A	175 A	Service entrance
4/0 AWG	150 A	180 A	205 A	Main service feeders

🧰 Quick comparison (Copper vs Aluminum):

AWG	Copper (75°C)	Aluminum (75°C)
14	20 A	— (no AL wire this small)
12	25 A	20 A
10	35 A	30 A
8	50 A	40 A
6	65 A	50 A
4	85 A	65 A
2	115 A	90 A
1/0	150 A	120 A
4/0	230 A	180 A

⚠️ Important notes:

Aluminum wire must use anti-oxidation compound and AL/CU-rated terminals.
Always size breakers and fuses according to NEC Table 310.16 (and check derating if wires are bundled or in hot areas).
For house wiring, copper is preferred for small circuits (≤10 AWG).

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