Guide · June 22, 2026
The steel box that made global trade cheap. Here's what's standard, what the variations are for, and how one container moves across three modes without ever being unpacked.
An intermodal container is a standardized steel box built to move between ships, trains and trucks without the cargo inside ever being unloaded. "Intermodal" means exactly that — multiple modes, one container. Its corner castings and dimensions follow an ISO standard, which is why a box loaded in Shenzhen locks onto a vessel, a rail well car and a truck chassis in Tacoma without anyone re-handling what's inside. That standardization is the whole reason ocean freight is as cheap as it is.
Almost all the containers you'll see come in a handful of standard sizes:
| Container | External length | Notes |
|---|---|---|
| 20 ft (TEU) | 20' | The base unit — "TEU" (twenty-foot equivalent) is how ports count volume. |
| 40 ft (FEU) | 40' | The most common box in global trade; two TEU. |
| 40 ft High Cube | 40' | Same footprint, one foot taller (9'6") for more cube. |
| 45 ft High Cube | 45' | Extra length for light, high-volume freight. |
A 20 ft box typically holds around 10 standard pallets and a 40 ft about 20–24 — though weight limits often fill up before the floor does, especially with dense product.
Beyond size, containers vary by what they're built to carry:
The open-top and flat-rack boxes are where cargo often becomes out-of-gauge — wider, taller or heavier than a standard load — which moves under permits as project and heavy-haul freight.
Follow a single 40 ft box from origin to door:
At no point in that chain does anyone open the box — until it reaches a warehouse and the freight is unloaded or transloaded into domestic trailers or trucks for final distribution.
The Northwest Seaport Alliance — the combined Ports of Seattle and Tacoma — is one of the largest container gateways in North America. For an importer, the practical question isn't the ocean leg (the steamship line handles that); it's the inland move: who pulls the box, tracks its free time, and gets it unpacked without a storage bill. Running drayage and the warehouse together is how we keep that last stretch tight for customers like PartStop, from the terminal straight into stored, sorted inventory.
A standardized steel shipping container built to ISO dimensions so it can move between ship, rail and truck without the cargo inside being unloaded or repacked.
The common sizes are 20 ft, 40 ft, 40 ft high cube and 45 ft high cube. The 20 ft box is the base "TEU" unit ports use to count volume; the 40 ft is the most widely used.
A TEU is a twenty-foot equivalent unit (a 20 ft container); an FEU is a forty-foot equivalent unit (a 40 ft container, equal to two TEU). Ports report throughput in TEU.
One container moves across multiple modes — typically ocean, then rail, then truck (drayage) — without the cargo being handled in between, until it reaches its destination warehouse.
Drayage is the short truck move that connects the ocean or rail terminal to the local warehouse or door — the final inland leg of an intermodal journey.