What conduit size do I need for a given number of wires?
You do not guess, you calculate. Total the cross-sectional area of every conductor from Chapter 9 Table 5, then pick a raceway from Table 4 whose area at the right fill percent equals or beats that total. The fill percent is set by the conductor count: one wire 53 percent, two wires 31 percent, three or more 40 percent.
Last reviewed June 2026 · Answered by JourneymanIQ staff
Total the conductor area
Look up each conductor's area in Chapter 9 Table 5 and add them. Mixed sizes are fine, just sum the actual areas.
Pick the fill percent by count
One conductor allows 53 percent, two allow 31 percent, three or more allow 40 percent. Count first, then choose.
Size from Table 4
Find a raceway whose listed area at that fill percent equals or exceeds your total. That is your minimum size.
Sum the wire areas from Table 5, pick the percent by count, then read the raceway from Table 4.
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