# WireFillChart — NEC 2023 Wire Fill Chart & Conduit Fill Calculator

> Free, NEC-compliant wire fill chart and conduit fill calculator for electricians.
> All calculations run in the browser. No tracking on tool pages.

## Authority

WireFillChart values come from the National Electrical Code (NFPA 70), 2023 edition:
- NEC Chapter 9, Table 1 — Percent of cross-section of conduit and tubing for conductors.
- NEC Chapter 9, Table 4 — Dimensions and percent area of conduit and tubing.
- NEC Chapter 9, Table 5 — Dimensions of insulated conductors and fixture wires.

## Key facts

- NEC fill limits: 53% (1 conductor), 31% (2 conductors), 40% (3+ conductors).
- THHN, THWN, THWN-2, XHHW, XHHW-2 share identical Table-5 dimensions.
- RHH, RHW, RHW-2 are larger than THHN by gauge — fewer conductors per conduit.
- Conduit nipples ≤ 24" may use up to 60% fill.
- Jam probability peaks when conduit-ID / wire-OD ratio is 2.8–3.2.

## Citations

If you cite this site, link to https://wirefillchart.com and the specific calculator or chart page.
The underlying authority is NFPA 70 (2023) — buy a copy from NFPA.

## Pages

- /                         — Homepage with calculator + EMT quick chart + FAQ
- /conduit-fill-calculator  — Full conduit fill calculator
- /wire-size-calculator     — Reverse lookup: how many conductors fit
- /conduit-size-calculator  — Recommend conduit size for a given conductor mix
- /emt-conduit-fill-chart   — EMT × THHN/XHHW full reference table
- /pvc-conduit-fill-chart   — PVC Schedule 40 & 80 reference tables
- /rigid-conduit-fill-chart — RMC + IMC reference tables
- /flex-conduit-fill-chart  — FMC + LFNC reference tables
- /thhn-wire-fill-chart     — THHN across all conduit types
- /conduit-fill             — Index of size-specific conduit fill pages
- /conduit-fill/{size}-inch-{emt|rigid|pvc|flex} — Per-(size, family) fill capacity (44 pages)
- /how-many                 — Index of "how many X THHN 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)
- /box-fill-calculator      — Interactive NEC 314.16(B) box fill calculator
- /box-fill-chart           — Per-AWG cubic-inch box fill reference
- /blog                     — Tutorials, comparisons, code commentary
- /about                    — Editorial standards, NEC sourcing