Multi-skid cubic feet, density, linear foot & penalty engine
- Safe — tariff cube, density and linear feet stay under the carrier's cube and linear-foot rules.
- Tier 1 — 350 cu ft or more under 3 PCF (XPO, Saia, ABF, Estes): synthetic weight of 6 lbs per tariff cubic foot.
- Re-bill — 750 cu ft or more under 6 PCF, or linear feet at the carrier's rule: book volume LTL or direct partial truckload.
How the engine measures a load
Every LTL bill starts from three numbers the carrier can verify with a tape, a scale or an overhead laser: the outside dimensions of each handling unit, the weight of each unit including its pallet, and whether anything may be loaded on top of it. The engine asks for exactly those numbers, line by line, because mixed loads are the norm on a shipping dock — six standard 48×40 skids and two long crates do not average into one "typical" pallet.
Measure at the outermost points. If cartons hang two inches past the deck boards, the unit is 52 inches long, not 48. If shrink-wrap balloons over a top tier, measure the bulge. Carriers' dimensioners photograph the silhouette of the whole unit, and the bill follows the silhouette.
The weight field takes either the weight of each unit or the total for the line, in pounds or kilograms, and the +40 lb skid button adds a typical hardwood GMA pallet's tare to each unit — the most common reason a shipper's declared density is lower than the carrier's scale ticket.
Actual cube vs. tariff cube: the phantom cubic feet
The second readout, tariff (imputed) cube, is where most re-bills come from. When a unit is marked "Do Not Double-Stack", has a pyramid or cone top, or is taller than about 60 inches, nothing can ride on it inside a trailer with a 96–110 inch interior. Carrier rules tariffs therefore charge the space above it: the unit is cubed as if it were 96 inches tall.
Take the preset load: eight non-stackable 48×40 skids, 66 inches tall, 290 lbs each.
| Measure | As shipped | As the carrier cubes it |
|---|---|---|
| Height per unit | 66 in | 96 in |
| Cubic feet per unit | 73.3 | 106.7 |
| Total cubic feet (8 units) | 586.7 | 853.3 |
| Total weight | 2,320 lbs | 2,320 lbs |
| Density | 3.95 PCF | 2.72 PCF |
| NMFC 13-tier class | 250 (Sub 3) | 250 (Sub 3) |
The load gains 266.7 phantom cubic feet. At 853 tariff cubic feet and under 6 PCF it crosses the 750 cu ft cubic capacity threshold that every major LTL carrier publishes; it also crosses XPO's 350 cu ft / 3 PCF tier. That is why the badge turns red even though the bill of lading looked like an ordinary eight-pallet LTL shipment.
NMFC 13-tier class assignment and the next cheaper tier
Class comes from density for most freight under the NMFC 13-subprovision scale published through NMFTA Docket 2025-1. The engine maps actual PCF and tariff PCF to their subprovisions separately, so you can see when imputation alone pushes a load into a worse class.
| Sub | Density (PCF) | NMFC class | Typical commodities |
|---|---|---|---|
| Sub 1 | Less than 1 | 400 | Assembled kayaks, expanded polystyrene, lampshades |
| Sub 2 | 1 to under 2 | 300 | Fiberglass insulation batts, assembled wicker furniture, empty plastic tanks |
| Sub 3 | 2 to under 4 | 250 | Mattresses, HVAC spiral ductwork, upholstered seating |
| Sub 4 | 4 to under 6 | 175 | Assembled office cabinets, medical carts, refrigeration shells |
| Sub 5 | 6 to under 8 | 125 | Crated small pumps, vending machines, range hoods |
| Sub 6 | 8 to under 10 | 100 | Wine and beverage cases, auto body panels, boxed electronics |
| Sub 7 | 10 to under 12 | 92.5 | Commercial kitchen appliances, crated motors, boxed hardware |
| Sub 8 | 12 to under 15 | 85 | Machine parts, boxed tools, compressors, transmissions |
| Sub 9 | 15 to under 22.5 | 70 | Palletized canned goods, machinery components, cable reels |
| Sub 10 | 22.5 to under 30 | 65 | Bottled beverages, ceramic tile, boxed fasteners, dry chemicals |
| Sub 11New | 30 to under 35 | 60 | Sheet steel, bagged cement and mortar, lead-acid batteries |
| Sub 12New | 35 to under 50 | 55 | Bricks, hardwood flooring bundles, bar stock, brass fittings |
| Sub 13New | 50 or more | 50 | Steel coils, castings, bulk fasteners in kegs, granite slabs |
NMFC 13-subprovision density scale (NMFTA Docket 2025-1). Density = total weight including pallet ÷ total cubic feet. Commodity-specific NMFC items can still override density for some articles.
Under the class readout the engine shows the next density bracket up and two ways to reach it: pounds of freight you could consolidate onto the same units, or cubic feet you would have to remove — expressed as inches off every unit's height if the units are uniform. Trimming 4 inches of empty corrugated off a top tier is often cheaper than any rate negotiation.
Linear feet and trailer utilisation
Carriers also rate by floor space. Two 40- or 48-inch-wide units fit side by side in a 96–102 inch trailer, so a line of 48-inch-long non-stackable skids uses one row (4 linear feet) for every two units. Stackable units no taller than 60 inches can go two high, halving the rows.
The utilisation bars compare that footprint with a 26-foot straight truck and a 52.5-foot usable 53-foot van. Once a load passes roughly 12 linear feet, most carriers' linear-foot rules allow them to re-rate it as a capacity or volume shipment — the engine flags it against the chosen carrier's threshold (12 LF for most, 15 LF for Old Dominion).
The penalty badge and mode comparison
- Green — standard LTL safe: tariff cube under the carrier's triggers, density above them, and linear feet under the rule.
- Amber — tier 1 low-density trigger: 350 cubic feet or more under 3 PCF for carriers that publish a first tier (XPO, Saia, ABF, Estes). The engine shows the synthetic weight: tariff cube × 6 lbs.
- Red — cubic capacity or linear-foot re-bill: 750 cubic feet or more under 6 PCF, or linear feet at or above the carrier's rule. The engine estimates the re-bill and recommends a mode.
The mode table prices the same freight six ways on the miles you set: base LTL tariff, LTL after a cube re-bill, spot volume LTL, direct partial truckload, a dedicated 26-foot box truck and a 53-foot truckload. These are indicative planning figures from the Cubic Transport model with fuel included; tendered rates depend on lane, date, accessorials and carrier capacity. Spot volume quotes are shown only up to about 28 linear feet and 20,000 lbs, the usual ceiling of carrier volume desks.
Share the load, print the manifest, lock the rate
- Copy the shareable load link. Every input is written into the page address (
?qty=8&l=48&w=40&h=66&wt=290&stack=0&carrier=xpo&miles=900), so a colleague or carrier rep opens the identical calculation. - Print the BOL dimensional manifest. A one-page shipper dimensional verification and NMFC 13-tier certificate with every line, total cube, density, class, linear feet and signature blocks. Staple it to the bill of lading and photograph each unit with a tape against it; that pairing is what wins W&I disputes.
- Lock a direct PTL or volume LTL rate. The button copies the full load summary into the tender form below so the rate desk receives the same figures you see.
Related tools: the linear foot calculator for floor plans, the CBM converter for metric and import freight, and the LTL vs. partial truckload analyzer for break-even points.