Freight Class for Cardboard Boxes
Flat cardboard is denser freight than most people expect. Banded e-commerce mailers measured 24.0 lb/ft³, which is class 65 on the current NMFC scale. A bundle of 25 flat moving boxes measured 11.2 lb/ft³, class 92.5, and a pallet of mixed box kits 9.8 lb/ft³, class 100. Assembled boxes are mostly air and rate far higher, around class 300.
Cardboard ships denser than its reputation
Cardboard has a reputation as miserable freight, and it's half-earned — but only half. Flat cardboard is thin sheets of solid paperboard, and thin flat things bundle into surprisingly dense stacks: a banded brick of mailers or folding cartons can measure over 20 lb/ft³, right down with bottled goods in the cheap classes. The miserable version is cardboard with its shape restored — assembled gift boxes, erected shippers, loose piles — where the freight is again mostly the air the boxes were designed to hold.
The other cardboard-specific variable is the size mix. Moving kits and retail box assortments bundle small, medium and large flats together, and mismatched flat sizes stack like a badly shuffled deck — edges overhanging, voids between bundles. Sorting flats by footprint before banding, or banding assortments so that same-size flats nest within each bundle, keeps an assorted shipment measuring close to what uniform stock would.
Worked examples
Measured as shipped: the outside of each bundle or the loaded pallet, and the total weight.
Banded e-commerce mailers — class 65
A tight brick of 200 flat mailers, 18" × 12" × 14", 42 lb.
18 × 12 × 14 = 3,024 in³ ÷ 1,728 = 1.75 ft³. Density = 42 lb ÷ 1.75 ft³.
24.0 lb/ft³ → class 65 — flat thin board is dense freight.
A bundle of 25 flat moving boxes — class 92.5
One banded bundle of KD medium moving boxes, 24" × 18" × 10", 28 lb.
24 × 18 × 10 = 4,320 in³ ÷ 1,728 = 2.5 ft³. Density = 28 lb ÷ 2.5 ft³.
11.2 lb/ft³ → class 92.5.
Palletized mixed box kits — class 100
Assorted-size flat bundles stacked 48" high on a 48" × 40" pallet, 520 lb.
48 × 40 × 48 = 92,160 in³ ÷ 1,728 = 53.3 ft³. Density = 520 lb ÷ 53.3 ft³.
9.8 lb/ft³ → class 100. Size-sorting the bundles tighter pushes this toward 92.5.
Kits, mailers, and the assortment problem
E-commerce mailers and folding cartons are the best-case cardboard: small, uniform, thin, and dense in high-count bundles. If mailers are part of a mixed shipment, band them as their own bricks and use them the way a dense commodity is always used — as ballast that raises the whole pallet's blended density.
Moving-box kits sold as retail units bring a subtler trap: the kit often includes tape, cushioning and a handle-carton that force a larger, half-empty master pack. Shipping kit master-packs as they land in retail inventory can rate two classes worse than shipping the same boxes re-bundled flat. When volume justifies it, break kits to flats for the linehaul and re-kit at destination — and let the calculator below price the difference for your actual counts.
Check your cardboard shipment's class
Enter the bundle or pallet size and the total weight. Keep bundles the same size so the stack measures as a tight block.
Density-based estimate. Some commodities carry a fixed NMFC class — check our freight class by commodity pages.
Estimated Freight Class
Density
26.25
lb/ft³
Volume
53.33
ft³
Weight
1,400
lb
22.5–30 lb/ft³ → Class 65
NMFC density scale (Docket 2025-1, effective July 19, 2025)
Free PDF includes a watermark. Pro removes it & adds your brand.
Estimates only — verify freight class/NMFC and chargeable weight with your carrier.
Uses the 13-tier NMFC density scale (Docket 2025-1). See the full freight class chart.
Frequently asked questions
What freight class are cardboard boxes?
Flat and banded, cardboard boxes usually rate class 65 to 100 on the current NMFC scale. Thin, flat mailers are the densest. Moving-box bundles and mixed kits sit near 92.5 to 100. Assembled boxes rate around class 300.
What freight class are cardboard boxes?
Flat and tightly bundled: commonly 9–12 lb/ft³ → class 92.5–100 palletized, and dense flat stock like mailers measures far better still. Assembled or loose boxes rate at the light-freight extremes. Flat versus assembled decides everything.
What's the cheapest way to ship moving boxes?
Knocked-down flat, banded into same-size bundles, stacked flush on a pallet. Retail kit master-packs with tape and cushioning inside rate worse — for volume moves, ship flats and re-kit at the destination.
Is cardboard classed differently from corrugated board?
For most shippers both are rated by density, so the same flat-versus-assembled rules apply. Thin folding-carton board bundles denser than fluted corrugated, so flat cardboard often measures a class better on the same footprint. A few paperboard items carry their own NMFC listing, which your carrier can check.