Sources
Every figure on this site comes from a document you can open, and this page lists those documents, states when each was last checked, and explains one deliberate omission that matters more than the rest of the page combined. If you are going to cite a density-to-class number, start here rather than with the number itself.
The two tables, and why we only use one
NMFTA publishes two density tables that look similar and are not the same. One is the 13-subprovision density scale used for classifying items; the other is the FCDC Density Guidelines, an 18-row internal category-assignment aid.
The guidance table covers class 50 through 500 and gives only a lower density bound per row. The classification scale covers class 50 through 400 and gives a bounded interval per row. In the ranges where they overlap, the two tables disagree.
As one concrete example, the guidance table assigns class 500 to freight under 1 lb/ft³, while the classification scale assigns class 400. In the 6-to-7 lb/ft³ range the guidance table gives 150 where the classification scale gives 125.
We use the classification scale, because that is the table that governs item classification. We are stating this at length because using the other table produces plausible-looking wrong answers in several bands, and because a site that had mixed them up would have no way to notice from the outside.
What we check, and which parts are automated
The data file carries the version identifier, the effective date, the primary source, and the date it was last verified against that source.
Automated checks run on every load and in continuous integration: the table must have contiguous half-open intervals with no gaps or overlaps, strictly increasing density bounds, strictly decreasing class values, exactly one open lower end and one open upper end, and no class value above 400 or below 50.
A separate check fails the build if a class value ever appears above 400, which is the signature of the guidance table being pasted in by mistake.
Those checks catch structural corruption. They do not catch a single plausible wrong number in the middle of the table, so each of the 13 rows is also pinned by a test that asserts the exact published value.
Archived copies
NMFTA publishes only the most recent docket on its public docket page, so earlier dockets can disappear from the primary location. We keep archived copies of the documents the data was taken from and link them below.
If you are citing this site for anything that matters, cite the primary source instead, and use our archived copy only if the original is no longer reachable.
Density class per NMFC Docket NMFC-2025-1 (NMFTA Disposition Bulletin 1371), effective 2025-07-19. Density scale: 13 subprovisions, class 50–400. Subject to NMFC Item (Rule) 170.
Frequently asked
Why not just use the table with more rows?
Because more rows is not more accuracy here. The two tables answer different questions, and only one of them governs item classification. The 18-row table is a category-assignment aid, not the classification scale.
Do you reproduce NMFC item numbers?
No. The NMFC code library is a paid NMFTA product, and this site deliberately does not reproduce it. What is reproduced is the published density-to-class relationship, which NMFTA and its members publish openly as part of the Docket 2025-1 changes.
What happens when NMFTA publishes a new docket?
The data file is versioned, so a change produces a new version rather than an edit in place. The version identifier and effective date shown on each page change with it, and the previous values are recorded so the change is visible.
Data source verified:
Primary source: NMFTA Disposition Bulletin 1371 — density and class breaks for the 13-subprovision structure
Archived copy: snapshot 0, snapshot 1