What is TEU? Twenty-Foot Equivalent Unit Explained

TEU stands for twenty-foot equivalent unit, the standard measure the container shipping industry uses to express capacity. The World Shipping Council, the trade association for liner carriers, defines it as the industry standard for measuring containers, based on a 20-foot container whose external dimensions of twenty feet long (6.09 metres), eight feet wide (2.4 metres) and eight feet six inches high (2.6 metres) were set by the International Organization for Standardization (World Shipping Council glossary). Maersk gives the same plain reading: TEU is an abbreviation of twenty-foot equivalent unit, in other words a twenty-foot container, and it can be used to measure vessel capacity (Maersk).

The unit exists because containers are not all the same length. A 40-foot box takes roughly twice the length of a 20-foot one, so counting boxes alone cannot summarise a mixed cargo. A common denominator turns any mix of sizes into one comparable figure, which lets carriers, terminals, ports and analysts discuss capacity and throughput in the same language.

TEU and FEU: the forty-foot box counts as two

The companion unit is the forty-foot equivalent unit, or FEU. The World Shipping Council defines an FEU as a container the same height and width as a TEU but twice the length, and therefore with twice the capacity (World Shipping Council glossary). A standard 40-foot container therefore counts as 2 TEU. Freightos states the relationship the other way round: two TEUs have the capacity of a single FEU (Freightos).

Container	Length	Nominal count	Note
20 ft standard	6.09 m	1 TEU	The reference box for the unit
40 ft standard	about 12.2 m	2 TEU, or 1 FEU	Twice the length, twice the count
40 ft high cube	about 12.2 m	2 TEU	Taller, but the same length count

What a TEU counts, and what it leaves out

A TEU counts nominal slots, not cargo. It says nothing about weight, usable volume, or the value of the goods inside: a container full of steel and a container full of light packaging count the same TEU if they are the same length. TEU is a capacity unit, so it answers how many standard boxes a ship, terminal or trade lane can move, not what those boxes weigh or what they are worth. The World Shipping Council describes TEU as a capacity measurement of containerised cargo, based on the volume of a standard 20-foot container, and notes that it is unique to container shipping (World Shipping Council).

Where TEU appears

• Vessel capacity. A container ship is described by the number of TEU it can carry. The World Shipping Council notes that deck-stowed containers on an 11,000 TEU vessel are stacked seven to eight high and nineteen across (World Shipping Council). See How container ships are sized for how those figures are set.
• Port throughput. Ports report annual volumes in TEU. Drewry’s Container Port Throughput Indices, for example, are built on monthly throughput data for a sample of over 340 ports worldwide, representing over 80 percent of global volumes (Drewry).
• Terminal design. Berths, cranes and yard layouts are planned against expected TEU flows, so a terminal brief is usually expressed in TEU per year rather than in boxes.
• Freight-rate contracts. Index-linked contracts reference TEU and FEU. Freightos notes that rates can be quoted per TEU, making a shipment total the rate per TEU times the number of TEUs (Freightos). Contracts mixing the two units need care, since 1 FEU is 2 TEU. Container freight rate indexes explained covers how those reference prices are assembled.

TEU is not tonnage

TEU and deadweight tonnage are often read together, but they measure different things. Deadweight tonnage (DWT) is a weight measurement of a ship’s maximum carrying capacity, covering everything it can hold besides its own empty weight (World Shipping Council). TEU is a count of slots, and neither converts into the other. A ship can be full by slot count yet well under its weight limit. A TEU figure will not tell you how much a vessel can lift, and a DWT figure will not tell you how many boxes fit.

Common misreadings

• TEU is not a container type. A TEU is not a box you can order; it is a unit of account. The physical container is a 20-foot ISO container.
• A 20-foot and a 40-foot container are not interchangeable. Both move on the same vessel, as the World Shipping Council describes when it notes ships generally carry a mix of 20-foot and 40-foot boxes, but a 40-foot box consumes two nominal TEU where a 20-foot box consumes one (World Shipping Council). Many ships also carry 45-foot and 48-foot boxes on deck, which complicates a simple slot count.
• TEU totals counted on different bases are not comparable.

Nominal, deployed and effective capacity

A TEU figure is only meaningful if it states which kind of capacity it describes, because the same ship can produce several different TEU numbers.

• Nominal capacity is the maximum a ship is designed to carry under ideal stowage, the headline figure in specifications and newbuilding orders.
• Deployed capacity is what a carrier actually assigns to a trade lane or service, rising and falling as ships are added or withdrawn.
• Effective capacity is what is genuinely available for cargo once port omissions, blank sailings, draft and berth limits, and the size mix on board are taken into account.

These numbers can differ widely. A vessel quoted at nominal capacity and a service described by weekly deployed capacity are not the same thing, and growth rates calculated on each will not match. Careful analysts compare nominal against nominal and effective against effective, which is why capacity announcements should always carry a qualifier.