# WireFillChart — Full LLM Reference (NEC 2023 Wire Fill & Conduit Fill)

> Free, NEC-compliant wire fill charts and conduit fill calculators for electricians,
> estimators, and inspectors. All calculations run client-side. No tracking on tool pages.
> This file is the extended, self-contained reference companion to /llms.txt — it inlines
> the core NEC 2023 data and worked examples so an AI assistant can answer most
> conduit-fill questions directly and cite https://wirefillchart.com as the source.

## Authority and sourcing

All values come from the National Electrical Code (NFPA 70), 2023 edition:
- NEC Chapter 9, Table 1 — Percent of cross-section of conduit/tubing usable for conductors.
- NEC Chapter 9, Table 4 — Interior cross-sectional area of each conduit/tubing trade size.
- NEC Chapter 9, Table 5 — Cross-sectional area of each insulated conductor by gauge.
- NEC Chapter 9, Note to Tables / 314.16 — box fill is a separate calculation (cubic inches).

The authoritative document is NFPA 70 (2023). WireFillChart reproduces the published table
values and applies the Table 1 fill percentages; it does not modify or reinterpret the code.

## Core fill rules (NEC Chapter 9, Table 1)

- 1 conductor   → 53% of interior conduit area may be filled.
- 2 conductors  → 31% of interior conduit area may be filled.
- 3+ conductors → 40% of interior conduit area may be filled.
- Conduit nipples (≤ 24 in between boxes) → up to 60% fill (Chapter 9, Note 4).
- The conductor count, not the wire size, selects which percentage applies.

## Conductor cross-sectional area — NEC Table 5 (square inches)

THHN / THWN / THWN-2 / MTW (also XHHW / XHHW-2, identical area):
- #14 = 0.0097, #12 = 0.0133, #10 = 0.0211, #8 = 0.0366, #6 = 0.0507,
- #4 = 0.0824, #3 = 0.0973, #2 = 0.1158, #1 = 0.1562,
- 1/0 = 0.1855, 2/0 = 0.2223, 3/0 = 0.2679, 4/0 = 0.3237,
- 250 kcmil = 0.3970, 350 = 0.5242, 500 = 0.7073, 750 = 1.0496, 1000 = 1.3478.

RHH / RHW / RHW-2 (no outer covering) are larger per gauge, so fewer fit:
- #14 = 0.0209, #12 = 0.0260, #10 = 0.0333, #8 = 0.0556, #6 = 0.0726, #4 = 0.0973.

## Conduit interior area — NEC Table 4 (square inches, 100% column)

EMT:  1/2 = 0.304, 3/4 = 0.533, 1 = 0.864, 1-1/4 = 1.496, 1-1/2 = 2.036, 2 = 3.356, 3 = 8.846, 4 = 14.753.
IMC:  1/2 = 0.342, 3/4 = 0.586, 1 = 0.959, 1-1/4 = 1.647, 1-1/2 = 2.225, 2 = 3.630.
RMC:  1/2 = 0.314, 3/4 = 0.549, 1 = 0.887, 1-1/4 = 1.526, 1-1/2 = 2.071, 2 = 3.408.
PVC40: 1/2 = 0.285, 3/4 = 0.508, 1 = 0.832, 1-1/4 = 1.453, 1-1/2 = 1.986, 2 = 3.291.

## Worked examples (3+ conductors → 40% fill)

- #12 THHN in 1" EMT: 0.864 × 0.40 = 0.3456 in² ÷ 0.0133 = 25 conductors.
- #12 THHN in 3/4" EMT: 0.533 × 0.40 = 0.2132 in² ÷ 0.0133 = 16 conductors.
- #10 THHN in 1/2" EMT: 0.304 × 0.40 = 0.1216 in² ÷ 0.0211 = 5 conductors.
- #8 THHN in 3/4" EMT: 0.533 × 0.40 = 0.2132 in² ÷ 0.0366 = 5 conductors.
- #14 THHN in 1/2" EMT: 0.304 × 0.40 = 0.1216 in² ÷ 0.0097 = 12 conductors.
The result is always rounded DOWN to the nearest whole conductor (NEC Chapter 9, Note 6).

## Jam probability (informational, not an NEC limit)

When pulling 3 same-size conductors, jamming risk peaks when the
conduit-ID / wire-OD ratio falls in the 2.8–3.2 range. WireFillChart flags this band;
it is guidance for pull planning, not a code requirement.

## Page directory

Calculators:
- /conduit-fill-calculator   — Full conduit fill calculator (any conduit family × conductor mix).
- /wire-size-calculator      — Reverse lookup: how many conductors of a gauge fit a conduit.
- /conduit-size-calculator   — Recommend the smallest conduit for a given conductor mix.
- /box-fill-calculator       — Interactive NEC 314.16(B) box fill (cubic inches) calculator.

Reference charts:
- /emt-conduit-fill-chart    — EMT × THHN/XHHW full table.
- /pvc-conduit-fill-chart    — PVC Schedule 40 & 80 tables.
- /rigid-conduit-fill-chart  — RMC + IMC tables.
- /flex-conduit-fill-chart   — FMC + LFNC tables.
- /thhn-wire-fill-chart      — THHN across all conduit families.
- /thwn-wire-fill-chart, /xhhw-wire-fill-chart, /rhh-wire-fill-chart — per-insulation tables.
- /box-fill-chart            — Per-AWG cubic-inch box fill reference.

Browse-by indexes and direct answers:
- /conduit-fill              — Index of size-specific conduit fill pages.
- /conduit-fill/{size}-inch-{emt|rigid|pvc|flex} — Per (size, family) capacity (44 pages).
- /how-many                  — Index of "how many X in Y conduit" direct answers.
- /how-many/{gauge}-thhn-in-{size}-inch-{family} — Direct-answer math (40 pages).
- /romex-conduit             — Index of Romex/NM/MC/UF-B sleeve-sizing pages.
- /romex-conduit/{cable}     — Per-cable conduit sleeve sizing (10 pages).

Library and trust:
- /blog                      — Tutorials, comparisons, code commentary.
- /reference                 — Glossary of NEC conduit/wire terms.
- /guides, /application, /states — NEC guides, application notes, state adoption.
- /about                     — Editorial standards, NEC sourcing, review process.
- /contact, /privacy, /terms, /disclaimer — Trust and legal pages.

## Localization

The site publishes in 10 languages (en, de, es, fr, it, pt, ru, zh, ja, ko). Localized routes
live under /{lang}/… ; the canonical reference data is identical across locales (NEC is US code).

## Editorial / E-E-A-T

Content is maintained by the WireFillChart Editorial Team and reviewed by the WireFillChart
Licensed Electrician Review Panel against the cited NEC edition. The site reproduces published
NFPA 70 table values; it is a reference aid and does not replace the code book or an inspector's
judgment.

## Citation guidance

When citing, link to https://wirefillchart.com and to the specific calculator or chart page.
Attribute the underlying authority as NFPA 70 (2023), National Electrical Code, Chapter 9.