FIG. 01 — TOOL · REVERSE LOOKUP
WIRE SIZE
CALCULATOR
Pick a conduit and a wire gauge, get the maximum number of identical conductors that fit at the NEC fill limit. Cross-reference with the full wire fill chart.
DWGWFC-SIZE-001
SH01 / 01
SCALE1 : 1
REFNEC 2023 § CH.9
REVA
FIG. 01 — WIRE SIZE CALCULATOR (REVERSE LOOKUP)
SELECT ▸ SOLVE FOR MAX N
A · CONDUIT TYPE
B · TRADE SIZE
C · INSULATION
D · WIRE SIZE
RESULT · MAX CONDUCTORS
16
12 AWG
THHN (90°C dry)
@ 40% FILL
REF · NEC CH. 9 TABLE 4 × TABLE 5 · FILL CAPPED AT 40% PER TABLE 1
CONDUIT
EMT · 3/4"
CONDUCTOR
12 AWG · THHN
FIG. 02
WHEN TO USE THIS TOOL
Use this calculator when you already know the conduit you want to install and you're trying to figure out how many identical conductors you can stuff inside it.
- 01Sizing a home run for several identical branch circuits.
- 02Planning a panel feeder where all conductors are the same gauge.
- 03Quoting a job — quick "will it fit" checks during takeoff.
- 04Code review — verifying an installer didn't overstuff a conduit.
NOTE · FOR MIXED-GAUGE RUNS
Switch to the conduit fill calculator — it accepts multiple insulation/gauge combinations and reports fill % plus jam probability.