NEC Table 310.16 Ampacity Chart Explained [2026]

NEC Table 310.16 is the most frequently referenced table in the National Electrical Code. It provides the allowable ampacity (current-carrying capacity) for insulated conductors rated up to 2000 volts, installed in raceways, cables, or directly buried.

The table covers conductor sizes from 14 AWG to 2000 kcmil for both copper and aluminium/copper-clad aluminium conductors. Values are given at three temperature ratings:

• 60°C column: Used for most 15A and 20A circuits where terminals are rated 60°C
• 75°C column: Used for circuits above 100A and for equipment with 75°C rated terminals
• 90°C column: Used for derating calculations only — the base ampacity before applying correction factors

All values assume an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a raceway or cable.

Using Table 310.16 correctly requires understanding the terminal temperature limitation rule (Section 310.14):

1. Determine the circuit amperage from the load calculation or overcurrent protection device rating.
2. Check terminal temperature ratings on both the equipment and the overcurrent device. For circuits ≤ 100A, assume 60°C unless marked otherwise (Section 110.14(C)(1)(a)).
3. Select the correct column based on the lowest terminal temperature rating in the circuit.
4. Find the conductor size whose ampacity in that column meets or exceeds the required amperage.
5. Apply correction factors if ambient temperature exceeds 30°C (Table 310.15(B)(1)) or if more than 3 current-carrying conductors share a raceway (Table 310.15(C)(1)).

Critical rule: When applying correction factors, you may use the 90°C column as the starting point for derating, but the final derated ampacity must not exceed the ampacity shown in the column matching the terminal temperature rating.

These are the copper conductor sizes engineers look up most frequently:

AWG/kcmil	60°C (A)	75°C (A)	90°C (A)	Typical Use
14 AWG	15	20	25	15A lighting circuits
12 AWG	20	25	30	20A general-purpose outlets
10 AWG	30	35	40	30A dryer, water heater
8 AWG	40	50	55	40-50A range, sub-panel
6 AWG	55	65	75	60A sub-panel feed
4 AWG	70	85	95	70-85A sub-panel
3 AWG	85	100	115	100A main service
2 AWG	95	115	130	100-115A service
1/0 AWG	125	150	170	150A service
2/0 AWG	145	175	195	175A service
4/0 AWG	195	230	260	200A main service

Note: The 60°C column governs most residential circuits. Use 75°C only when both the equipment and the overcurrent device are rated for 75°C.

Table 310.16 ampacities are valid only under standard conditions (30°C ambient, ≤3 conductors). Two sets of factors modify these values:

Temperature Correction (Table 310.15(B)(1))

For ambient temperatures above 30°C, multiply the table ampacity by the correction factor. For example, at 40°C the 75°C column factor is 0.88, reducing a 10 AWG conductor from 35A to 30.8A.

Conduit Fill Adjustment (Table 310.15(C)(1))

When more than 3 current-carrying conductors share a raceway or cable:

• 4-6 conductors: 80% of table value
• 7-9 conductors: 70%
• 10-20 conductors: 50%
• 21-30 conductors: 45%
• 31-40 conductors: 40%
• 41+ conductors: 35%

When both corrections apply, multiply: Adjusted Ampacity = Table Value × Temperature Factor × Fill Factor. Start from the 90°C column for maximum flexibility, but cap at the terminal temperature column value.

Engineers working across NEC and IEC/BS standards need to convert between AWG and metric (mm²) sizes:

AWG	mm²	Nearest Metric Standard
14	2.08	2.5 mm²
12	3.31	4 mm²
10	5.26	6 mm²
8	8.37	10 mm²
6	13.30	16 mm²
4	21.15	25 mm²
3	26.67	25 mm²
2	33.62	35 mm²
1/0	53.49	50 mm²
4/0	107.2	120 mm²

Important: AWG and metric sizes are not directly interchangeable. A 12 AWG conductor (3.31 mm²) has a different cross-section than a 2.5 mm² or 4 mm² metric conductor. Always use the correct standard’s ampacity table for the conductor you are installing.

Instead of manually looking up Table 310.16 and applying correction factors, use the ECalPro Cable Sizing Calculator. It automatically:

• Selects the correct ampacity column based on terminal temperature
• Applies ambient temperature correction per Table 310.15(B)(1)
• Applies conduit fill adjustment per Table 310.15(C)(1)
• Checks voltage drop per NEC Section 210.19(A)
• Generates a professional PDF report with all NEC references

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