Electricians
Wire Gauge Calculator
Find the correct AWG wire gauge for any amperage load based on NEC ampacity tables.
Based on NEC Table 310.16. Always use the next larger standard wire size when your exact amperage falls between table values. Apply correction factors for conduit fill, ambient temperature above 86°F, or long runs. Aluminum wiring requires special connectors and is not approved for all applications - consult local code.
Why wire gauge matters
Using the wrong wire gauge is a safety issue. Wire that is too small for the load will overheat, trip breakers, or worse, start a fire. Every circuit has a maximum amperage rating and the wire needs to be sized to handle that load safely. This calculator tells you the minimum wire gauge based on your amperage and distance so you stay within code.
Common wire gauge sizes for residential work
For most homes, 14 gauge wire handles 15 amp circuits. That covers general lighting and outlet circuits. 12 gauge handles 20 amp circuits for kitchens, bathrooms, and other dedicated circuits. 10 gauge is for 30 amp circuits like dryers and some AC units. 8 gauge handles 40 amp circuits and 6 gauge handles 50 amp circuits for ranges and large appliances.
Copper vs aluminum wire
Copper is the standard for residential wiring. It conducts better, is easier to work with, and connections are more reliable. Aluminum is cheaper and lighter, which is why it is used for service entrance cables and some larger feeders. If you are using aluminum, you need to go up a size compared to copper for the same amperage. This calculator accounts for both materials.
How distance affects wire sizing
The longer the wire run, the more voltage drops along the way. For short runs inside a house, the standard gauge for the amperage is usually fine. But for long runs to a detached garage, workshop, or well pump, you might need to go up a wire size to keep the voltage drop under 3 percent. This is where a lot of DIYers get tripped up.
Common Questions
Can I use 14 gauge wire on a 20 amp breaker?
No. 14 gauge wire is only rated for 15 amps. Putting it on a 20 amp breaker is a code violation and a fire hazard. Use 12 gauge minimum for 20 amp circuits.
What size wire do I need for an EV charger?
Most Level 2 EV chargers pull 40 amps and need 8 AWG copper on a 50 amp breaker. Check the charger specs because some pull 48 amps and need 6 AWG wire.
What wire size for a hot tub?
Most hot tubs need 6 AWG copper wire on a 50 amp GFCI breaker. Some smaller 120 volt hot tubs run on a regular 20 amp circuit with 12 gauge wire. Always check the hot tub manual first.
What is the difference between Romex and THHN wire?
Romex is a sheathed cable with multiple wires inside, used for running through walls and attics. THHN is individual wire you pull through conduit. You cannot run loose THHN through walls without conduit.
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