Conduit Fill Calculator - NEC Raceway Fill Percentages for THHN & XHHW

Oct 12, 2026

Conduit Fill Calculator provides raceway fill percentage values according to NEC for THHN and XHHW conductors. It includes two primary fill regimes (40% fill for over 2 wires and 60% fill for nipple conditions) with results by raceway type such as EMT, GRC, IMC, PVC40, PVC80, FLEX, and ST. It also supplies conductor square area data by AWG/kcmil and totals of conductor square area for varying conductor counts, supporting electrical estimating and sizing decisions for conduit systems.

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Raceway Fill Percentages as per NEC

40% Fill – Over 2 Wires

60% Fill – Nipple

Conductor Square Areas

Conductor square area by AWG / kcmil (THHN, XHHW)

Total square area by number of conductors (THHN)

Total square area by number of conductors (XHHW)

CONDUIT FILL CALCULATOR for THHN & XHHW Raceway Fill Percentages as per NEC | SIZE | 40% Fill – Over 2 Wires | | | | | | | 60% Fill – Nipple | | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | | EMT | GRC | IMC | PVC40 | PVC80 | FLEX | ST | EMT | GRC | IMC | PVC40 | PVC80 | FLEX | ST | | 1/2 | 0.122 | 0.125 | 0.137 | 0.114 | 0.087 | 0.127 | 0.125 | .182 | .188 | .205 | .171 | .130 | .190 | .188 | | 3/4 | 0.213 | 0.220 | 0.235 | 0.203 | 0.164 | 0.213 | 0.216 | .320 | .329 | .352 | .305 | .246 | .320 | .325 | | 1 | 0.346 | 0.355 | 0.384 | 0.333 | 0.275 | 0.327 | 0.349 | .519 | .532 | .575 | .499 | .413 | .490 | .524 | | 1 1/4 | 0.598 | 0.610 | 0.659 | 0.581 | 0.495 | 0.511 | 0.611 | .897 | .916 | .988 | .872 | .742 | .766 | .917 | | 1 1/2 | 0.814 | 0.829 | 0.89 | 0.794 | 0.684 | 0.743 | 0.792 | 1.221 | 1.243 | 1.335 | 1.191 | 1.027 | 1.115 | 1.188 | | 2 | 1.342 | 1.363 | 1.452 | 1.316 | 1.150 | 1.307 | 1.298 | 2.013 | 2.045 | 2.178 | 1.975 | 1.725 | 1.961 | 1.949 | | 2 1/2 | 2.343 | 1.946 | 2.054 | 1.878 | 1.647 | 1.963 | 1.953 | 3.515 | 2.919 | 3.081 | 2.817 | 2.471 | 2.945 | 2.929 | | 3 | 3.538 | 3.00 | 3.169 | 2.907 | 2.577 | 2.827 | 2.99 | 5.307 | 4.499 | 4.753 | 4.361 | 3.865 | 4.241 | 4.485 | | 3 1/2 | 4.618 | 4.004 | 4.234 | 3.895 | | 3.848 | 3.893 | 6.927 | 6.006 | 6.351 | 5.842 | | 5.773 | 5.839 | | 4 | 5.901 | 5.153 | 5.452 | 5.022 | 4.503 | 5.027 | 5.077 | 8.852 | 7.729 | 8.179 | 7.532 | 6.755 | 7.540 | 7.615 | | 5 | | 8.085 | | 7.904 | 7.142 | | | | 12.127 | | 11.856 | 10.713 | | | | 6 | | 11.663 | | 11.427 | 10.239 | | | | 17.495 | | 17.140 | 15.359 | | | Conductor Square Areas |
Conductor Square Area
| | | | | | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | |
AWG / kcmil | THHN | XHHW | AWG / kcmil | THHN | XHHW | | | THHN | XHHW
| | |
14 | 0.0097 | 0.0139 | 2 | 0.1158 | 0.1146 | |
300 | 0.4608 | 0.4536 | | |
12 | 0.0133 | 0.0181 | 1 | 0.1562 | 0.1534 | |
350 | 0.5242 | 0.5166 | | |
10 | 0.0211 | 0.0243 | 1/0 | 0.1855 | 0.1825 | |
400 | 0.5863 | 0.5782 | | |
8 | 0.0366 | 0.0437 | 2/0 | 0.2223 | 0.2190 | |
500 | 0.7073 | 0.6984 | | |
6 | 0.0507 | 0.0590 | 3/0 | 0.2679 | 0.2642 | |
600 | 0.8676 | 0.8709 | | |
4 | 0.0824 | 0.0814 | 4/0 | 0.3237 | 0.3197 | |
750 | 1.0496 | 1.0532 | | |
3 | 0.0973 | 0.0962 | 250 | 0.3970 | 0.3904 | |
1000 | 1.3478 | 1.3519 | | | Number of Conductors – Total Square Area – THHN | | | | | | | | | | | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | AWG | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | | 14 | 0.0097 | .019 | .029 | .039 | .049 | .058 | .068 | .078 | .087 | .097 | .107 | .116 | .126 | .136 | .146 | | 12 | 0.0133 | .027 | .040 | .053 | .067 | .080 | .093 | .106 | .120 | .133 | .146 | .160 | .173 | .186 | .200 | | 10 | 0.0211 | .042 | .063 | .084 | .106 | .127 | .148 | .169 | .190 | .211 | .232 | .253 | .274 | .295 | .317 | | 8 | 0.0366 | .073 | .110 | .146 | .183 | .220 | .256 | .293 | .329 | .366 | .403 | .439 | .476 | .512 | .549 | | 6 | 0.0507 | .101 | .152 | .203 | .254 | .304 | .355 | .406 | .456 | .507 | .558 | .608 | .659 | .710 | .761 | | 4 | 0.0824 | .165 | .247 | .330 | .412 | .494 | .577 | .659 | .742 | .824 | .906 | .989 | 1.071 | 1.154 | 1.236 | | Number of Conductors – Total Square Area – XHHW | | | | | | | | | | | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | AWG | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | | 14 | 0.0139 | .028 | .042 | .056 | .070 | .083 | .097 | .111 | .125 | .139 | .153 | .167 | .181 | .195 | .209 | | 12 | 0.0181 | .036 | .054 | .072 | .091 | .109 | .127 | .145 | .163 | .181 | .199 | .217 | .235 | .253 | .272 | | 10 | 0.0243 | .049 | .073 |

FAQs

What does the “40% Fill – Over 2 Wires” section provide?

It provides NEC-based raceway fill percentages for THHN and XHHW over 2 wires, organized by raceway type and conductor size.

What does the “60% Fill – Nipple” section provide?

It provides NEC-based raceway fill percentages for THHN and XHHW for nipple applications, again organized by raceway type and conductor size.

How are “Conductor Square Areas” and “Total Square Area” tables used?

They supply conductor square area values for THHN and XHHW by AWG/kcmil, and totals by the number of conductors, supporting conduit sizing and fill calculations.

Oct 12, 2026

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