NEC 310.16 Table Ampacity Chart 2026: Complete Reference Guide

As an electrical professional with over 15 years of experience, I’ve seen firsthand how proper conductor sizing prevents safety hazards and ensures code compliance. The NEC Table 310.16 is the most frequently referenced ampacity table in the National Electrical Code, used daily by electricians, engineers, and inspectors across the country.

NEC Table 310.16 provides allowable current-carrying capacities for insulated conductors based on wire size, material, and temperature rating. This table applies to conductors rated 0-2000 volts at 60°C, 75°C, and 90°C temperature ratings, assuming a 30°C ambient temperature and no more than three current-carrying conductors in a raceway.

After consulting with hundreds of electrical contractors and teaching dozens of apprentice classes, I’ve learned that mastering this table is essential for anyone working with electrical systems. This guide will help you understand and apply Table 310.16 correctly in real-world scenarios while ensuring NEC 2023 compliance.

Complete NEC Table 310.16 Data

The complete NEC Table 310.16 provides ampacity ratings for both copper and aluminum conductors across three temperature columns. Understanding how to read this table correctly is fundamental for proper conductor sizing in all electrical installations.

Size	Copper Conductors			Aluminum Conductors
AWG/kcmil	60°C	75°C	90°C	60°C	75°C	90°C
18 AWG	—	—	14	—	—	—
16 AWG	—	—	18	—	—	—
14 AWG	20	25	30	—	—	—
12 AWG	25	30	35	20	25	30
10 AWG	30	35	40	25	30	35
8 AWG	40	50	55	35	40	45
6 AWG	55	65	75	40	50	60
4 AWG	70	85	95	55	65	75
3 AWG	85	100	110	65	75	85
2 AWG	95	115	130	75	90	100
1 AWG	110	130	150	85	100	115
1/0 AWG	125	150	170	100	120	135
2/0 AWG	145	175	195	115	135	150
3/0 AWG	165	200	225	130	155	175
4/0 AWG	195	230	260	150	180	205
250 kcmil	215	255	290	170	205	230
300 kcmil	240	285	320	190	230	255
350 kcmil	260	310	350	210	250	280
400 kcmil	280	335	380	225	270	305
500 kcmil	320	380	430	260	310	350
600 kcmil	355	420	475	285	340	385
700 kcmil	385	460	520	310	375	425
750 kcmil	400	475	535	320	385	435
800 kcmil	410	490	555	330	395	445
900 kcmil	435	520	585	355	425	480
1000 kcmil	455	545	615	375	445	500
1250 kcmil	495	590	665	405	485	545
1500 kcmil	525	625	705	435	520	585
1750 kcmil	545	650	735	455	545	615
2000 kcmil	555	665	750	470	560	630

How to Apply Temperature Correction Factors?

The ampacity values in Table 310.16 are based on a standard 30°C (86°F) ambient temperature. When actual ambient temperatures differ from this standard, you must apply correction factors from NEC Table 310.15(B)(1). This is critical for ensuring conductor safety and code compliance.

Ambient Temperature (°C)	60°C Column	75°C Column	90°C Column
21-25	1.08	1.05	1.03
26-30	1.00	1.00	1.00
31-35	0.91	0.94	0.96
36-40	0.82	0.88	0.91
41-45	0.71	0.82	0.87
46-50	0.58	0.75	0.82
51-55	0.41	0.67	0.76
56-60	—	0.58	0.71
61-65	—	0.47	0.65
66-70	—	0.33	0.58
71-75	—	—	0.50
76-80	—	—	0.41

Calculation Example

Let’s walk through a practical example. You need to install 4 AWG THHN copper conductors in an attic with a 40°C ambient temperature:

1. Base ampacity from Table 310.16: 4 AWG copper = 95 amps (75°C column for THHN)
2. Apply temperature correction factor: At 40°C, the correction factor is 0.88 for the 75°C column
3. Calculate corrected ampacity: 95 × 0.88 = 83.6 amps
4. Round down to nearest standard: 83 amps

This corrected ampacity of 83 amps is now your maximum allowed current before applying any additional derating factors.

How to Use Table 310.16 in Real-World Scenarios?

Understanding how to apply Table 310.16 in practical situations is essential for electrical professionals. I’ve encountered numerous scenarios where proper application of this table prevents safety hazards and ensures National Electrical Code requirements are met.

Residential Applications

For residential wiring, most electricians use the 60°C column for older installations and the 75°C column for newer systems with modern equipment. However, there are important exceptions:

• NM Cable (Romex): Use the 60°C column for NM-B cable rated at 60°C
• THHN/THWN: Use the 75°C column when terminations are rated for 75°C
• Service entrances: Often use the 75°C column with proper terminations

Commercial and Industrial Applications

Commercial installations often allow for higher temperature ratings, making the 90°C column applicable. However, the termination temperature rating (typically found in NEC 110.14(C)) often limits you to the 75°C column regardless of conductor rating.

Derating for Multiple Conductors

When you have more than three current-carrying conductors in a raceway or cable, you must apply adjustment factors from NEC 310.15(C)(1):

• 4-6 conductors: 80% adjustment
• 7-9 conductors: 70% adjustment
• 10-20 conductors: 50% adjustment

NEC Code Changes: Table 310.15(B)(16) vs Table 310.16

Many electricians still refer to “Table 310.15(B)(16)” from earlier NEC editions. In the 2026 NEC cycle, this table was renumbered to Table 310.16 as part of a comprehensive restructuring of Article 310. This change restored the beloved title of the most commonly used ampacity table.

The table content remains essentially unchanged, but the reorganization improves code navigation and consistency. Always verify you’re using the correct table reference for your adopted NEC edition.

Common Mistakes When Using Table 310.16?

After reviewing hundreds of installations and training dozens of electricians, I’ve identified these common errors that can lead to code violations and safety hazards:

1. Using the wrong temperature column: Always verify conductor and termination temperature ratings before selecting a column
2. Ignoring ambient temperature corrections: Apply correction factors before derating for conductor count
3. Forgetting neutral conductor consideration: In certain scenarios, neutral conductors count as current-carrying
4. Mismatching copper and aluminum ratings: Never use copper ampacity values for aluminum conductors
5. Overlooking continuous load requirements: Continuous loads must be calculated at 125% of the load

Frequently Asked Questions

Final Recommendations

Mastering NEC Table 310.16 is essential for electrical safety and code compliance. Based on my experience teaching and applying these principles, here are the key takeaways:

Best Overall Approach: Always start by identifying your conductor type, material, and termination temperature rating before selecting the appropriate column. Then apply temperature correction factors before any derating adjustments.

Most Common Application: For residential work with THHN/THWN conductors and modern equipment, the 75°C column typically applies, but always verify termination ratings per NEC 110.14(C).

Safety First: When in doubt, use the more conservative value. It’s better to oversize conductors than to risk overheating and potential fire hazards.

Remember that this table is just one part of conductor sizing – always consider voltage drop, continuous load requirements, and local code amendments in your calculations. With proper application of Table 310.16 and related NEC requirements, you’ll ensure safe and code-compliant electrical installations.