NEC Table 310.16 — Wire Ampacity Chart

What is NEC Table 310.16?

NEC Table 310.16 is the most-referenced table in the National Electrical Code. It lists allowable ampacities for insulated conductors rated up to and including 2000 volts, installed in raceways, cables, or directly buried. The table covers conductor sizes from #14 AWG through 2000 kcmil for both copper and aluminum conductors at three standard temperature ratings: 60°C, 75°C, and 90°C. The 75°C column is the most commonly used in commercial and residential work because it matches the temperature rating of most terminations and equipment.

How to Read the Ampacity Table

To find the ampacity of a conductor, start with the wire gauge in the leftmost column. Move across to the column matching your conductor material (copper or aluminum) and the temperature rating of both the conductor insulation and the equipment terminals — whichever is lower governs. For example, THHN wire is rated 90°C, but if it terminates on a breaker rated 75°C, you must use the 75°C ampacity column. The values in this table assume no more than three current-carrying conductors in a raceway and an ambient temperature of 30°C (86°F). For higher conductor counts or ambient temperatures, apply the derating factors from NEC Tables 310.15(C)(1) and 310.15(B)(1).

When to Use This Table

Electricians and engineers reference NEC Table 310.16 any time they need to verify that a conductor can safely carry the expected load current. Common applications include:

• Branch circuits — sizing wire for receptacle, lighting, and appliance circuits to match the overcurrent protection device.
• Feeder conductors — selecting wire for panels and sub-panels based on calculated load and required ampacity after derating.
• Service entrance conductors — ensuring the conductors from the utility meter to the main disconnect meet the full calculated load of the building.

For voltage drop verification, pair this table with the voltage drop calculator. To find the minimum wire size for a given load, use the wire size calculator.