The Master
Conduit Fill Chart
The most comprehensive visual reference for conduit fill ratio charts. Based on NEC Chapter 9 standards, this chart helps you quickly verify your electrical conduit fill requirements.
Table 1 NEC Chapter 9 conduit fill ratio chart (Percent of Cross-Sectional Area)
Percent of cross-sectional area of conduit and tubing for conductors, % 31% 40% fill rules.
| Conductors in Raceway | Maximum Area Allowed (%) | Application |
|---|---|---|
| 1 Conductor | 53% | Single Phase / Grounds |
| 2 Conductors | 31% | Low-Jam Risk |
| 3 or More Conductors | 40% | Standard Code Standard |
Visual Comparison
The reason the limits vary isn't arbitrary. It's about how conductors' physical presence affects conduit fill percentage and thermal air gaps.
1 Wire: Most surface area, easiest conduit pull, highest NEC conduit fill percentage table and high cooling capacity.
2 Wires: High risk of 'twisting jamming' in bends, necessitating a stricter NEC conduit fill ratio chart % 31% fill rule limit.
3+ Wires: The balanced standard for multicore pulls and commercial power runs using the conduit fill percentage table.
Quick Capacity Reference
Standard EMT (Metallic Tubing) conduit fill chart 40% fill area reference for trade sizes.
How to Use This Data
Using this conduit fill ratio chart correctly depends on three factors of your specific build.
Wire Selection
Check Table 5 for diameter first.
Calculated Sum
Add all areas to find Total A.
Compliance Check
Compare conduit fill ratio chart to max allowed values below.
Quick Example
If your wires sum to 0.15 in², you must use at least a 3/4" Hub (which allows 0.203 in²).