Conduit Size Calculator
Enter how many wires you are pulling, their gauge and the conduit type. The calculator adds up the wire area, applies the NEC fill limit and picks the smallest trade size that passes.
- NEC Chapter 9 fill
- EMT, PVC and rigid
- Fill percentage shown
For THHN and THWN-2 copper wire, all the same size. Count every conductor, including neutrals and the ground wire.
Conduit can only be filled to 40% with three or more wires. Wires need space to be pulled in without damaging the insulation and to let heat escape. The electrical code limits fill to 53% of the conduit's inside area for one wire, 31% for two and 40% for three or more.
EMT conduit fill chart
Maximum THHN wires at 40% fill. Search for a size.
| EMT size | 14 AWG | 12 AWG | 10 AWG | 8 AWG | 6 AWG |
|---|---|---|---|---|---|
| 1/2 in | 12 | 9 | 5 | 3 | 2 |
| 3/4 in | 22 | 16 | 10 | 6 | 4 |
| 1 in | 35 | 26 | 16 | 9 | 7 |
| 1-1/4 in | 61 | 45 | 28 | 16 | 12 |
| 1-1/2 in | 84 | 61 | 38 | 22 | 16 |
| 2 in | 138 | 101 | 63 | 36 | 26 |
From NEC Annex C, Table C.1. PVC Schedule 40 holds slightly fewer wires because its walls are thicker.
Wire count and fill
12 AWG THHN in EMT. Slide the number of wires.
More than nine current-carrying wires in one conduit also need their ampacity derated, which can mean a bigger wire size.
How to size conduit
Areas, then the limit. Step through it.
Count conductors
All hots, neutrals and grounds.
Long runs with many bends are hard to pull at full fill. Going up one trade size makes pulling far easier.
EMT, PVC or rigid
Three common conduit types. Compare them.
Thin-wall steel, light and easy to bend. The usual choice indoors.
Plastic, corrosion-proof and glued together. Common underground.
Thick galvanised steel with threaded joints. The toughest option.
Rigid metal conduit is required in some hazardous and exposed locations. Check local code for where each type is allowed.
Before pulling wire
A smoother pull. Tick each item.
Tick each item as you go.
No more than 360 degrees of bends are allowed between pull points. Add a pull box if your run has more.
What you get
Size and how full it is. Each tile explains one result.
Smallest conduit that passes.
Total of all conductors.
Percent of the inside area used.
53%, 31% or 40% by count.
EMT, PVC or rigid.
Trade sizes are nominal. A 1/2 in EMT is actually about 0.62 in inside diameter.
Frequently Asked Questions
No question matches that search.
How many 12 AWG wires fit in 1/2 inch EMT?
Nine THHN wires at 40% fill.
What is the 40% conduit fill rule?
With three or more wires, they may take up no more than 40% of the conduit's inside area.
Do ground wires count toward conduit fill?
Yes. Every conductor in the conduit counts.
How many 10 AWG wires in 3/4 inch EMT?
Ten THHN wires.
Is PVC conduit fill different from EMT?
Yes. Schedule 40 PVC has a slightly smaller inside area, so it holds a few fewer wires.
What size conduit for 6 AWG wire?
Three 6 AWG and one 10 AWG ground fit in 3/4 in EMT. Use the calculator for your mix.
Can I overfill conduit if the run is short?
Nipples under 24 in may be filled to 60%. Longer runs follow the normal limits.
Pick conduit that passes and pulls
Add up the wire areas, apply the right fill limit and choose the smallest conduit that fits. Go up a size for long or bendy runs and the pull will be easier.
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