kVA Tools^BETA — Conduit Filler

The Conduit Filler calculates conduit fill % for mixed conductor lists auto-size, nipple exception, and jam ratio check, per NEC Chapter 9.

Project Title

Input — Conduit

Conduit Type

Trade Size

Nipple mode (≤ 24″) Auto-size

Input — Conductors

#	Wire Type (NEC Table 5)	Size	Quantity	Unit Area (in²)	Unit Area (mm²)	Unit Area (cm²)	Row Total (in²)

Areas from NEC 2026, Table 5. Fill limits from Table 1: 53% (1 conductor), 31% (2 conductors), 40% (3+). Nipple exception: 60% fill for raceways ≤ 24″ in length.

Output — Fill Results

Parameter	Value	Units
Total Conductor Area	—	in²
Conduit Internal Area	—	in²
Allowable Fill Area	—	in²
Fill Limit Applied	—
Fill Percentage	—	%
Total Conductors	—	—
Result	—

Output — Advisories

Check	Result
Minimum Passing Size / Auto-Size	—
Jam Ratio (advisory)	—
Future Fill Advisory	—

Jam ratio — informational only; not an NEC enforceable requirement (ref. NEC Annex C). Applies when exactly 3 identical conductors are pulled together. Ratio = conduit ID ÷ wire OD. Possible jam: 2.8–3.2. High risk: < 2.8.
Future fill: design practice is to limit actual fill to 40% to leave spare capacity.

NEC Reference

Conductors in Raceway	Max Fill	Source
1 conductor	53%	NEC Ch. 9 Table 1
2 conductors	31%	NEC Ch. 9 Table 1
3 or more conductors	40%	NEC Ch. 9 Table 1
Nipple ≤ 24″ (any count)	60%	NEC Ch. 9, Table 1 Notes

Conduit Application

Conduit Type	Sizes	Typical Environment	Typical Use	Key Traits
Electrical Metallic Tubing (EMT)	½″–4″	Dry indoor, exposed	Branch circuits, lighting	Light steel, easy bend, economical
Intermediate Metal Conduit (IMC)	½″–4″	Indoor/outdoor, damp	Feeders, service runs	Medium-wall steel, corrosion-resistant
Rigid Metal Conduit (RMC)	½″–6″	Harsh, hazardous	Services, industrial feeders	Thick-wall steel, max protection
PVC Schedule 40 / 80	½″–6″	Underground, wet	Buried feeders, duct banks	Nonmetallic, corrosion-proof
High-Density Polyethylene (HDPE)	½″–4″	Underground duct	Utility, telecom, fiber	Flexible, smooth interior
Liquidtight Flexible Metal Conduit (LFMC)	⅜″–4″	Wet, vibrating	Motors, HVAC, equipment	Flexible, liquidtight jacket
Electrical Nonmetallic Tubing (ENT)	½″–2″	Concealed indoor	Residential branch wiring	Flexible plastic, fast install

Input — Annex C Lookup

Conduit Type
Wire Type
Wire Size
Quantity

Annex C tables assume all conductors are identical, standard concentric stranded, at NEC Chapter 9 Table 1 fill limits. Compact stranded conductors (Tables C.x(A)) are not included.

Output — Annex C Result

Minimum conduit size	—
Reference	—

Conduit size	Max conductors	Fits qty?

NEC 2026, Annex C is informational. Where the calculated fill method (Tab 1) and Annex C yield different results, the calculated method governs.

kVA ToolsBETA — Conduit Filler