What Is a Cargo Ship? Types, Size, and How to Track One
In this article 9 sections
A cargo ship is any vessel built to carry freight rather than passengers, and most of what reaches a store shelf travels on one at some point. Roughly 90 percent of world trade by volume moves by sea. Most of that is cargo ships of one kind or another: container ships stacked with boxes, bulk carriers full of grain or iron ore, tankers moving oil and chemicals, general cargo ships taking whatever does not fit a standard container. The term covers a wider family of vessels than most people assume. The differences between them are also why a ship tracker shows some information about a voyage and stays completely silent about others.
What Is a Cargo Ship, Exactly?
Stripped down, a cargo ship is a hull, an engine room, and cargo space built around what it carries. A container ship has a grid of cells sized for twenty and forty foot boxes. A bulk carrier has open holds shaped to pour grain or ore in without bridging or shifting.
A tanker is mostly tank space threaded with pumps and piping. Naval architects call this the ship’s “type,” and it decides everything from hull shape to safe speed. No single hull does all three jobs well, which is why the types exist.
People also call a cargo ship a freighter or a merchant vessel. None of these names is wrong; they describe the same thing from different angles: cargo ship by function, freighter by trade usage, and merchant vessel by its legal status as commercial shipping rather than naval or fishing.
The category excludes only a few things. Passenger ships and cruise liners are built around berths and public rooms, not holds, even though some older ocean liners also carried mail and freight. Fishing vessels, tugs, and naval ships are separate categories, defined by what they do. Anything else that crosses open water carrying someone else’s goods for payment is, broadly, a cargo ship.
The Main Types of Cargo Ships
Ask how many types of cargo ships there are and you will get a different number depending on how finely someone wants to split the category. For a working answer, five types cover almost everything afloat.
| Type | What it carries | How you’d recognise it |
|---|---|---|
| Container ship | Standardised 20ft and 40ft boxes | Stacked rectangular containers, often 8+ tiers high on deck |
| Bulk carrier | Unpackaged solids: grain, coal, iron ore, bauxite | Large hatch covers, a boxy hull with little deck clutter |
| General cargo / break-bulk | Machinery, steel coils, project cargo too big for a box | Deck cranes, smaller and older-looking than a container ship |
| Ro-Ro | Vehicles that drive on and off under their own power | A near-featureless slab-sided hull with a stern ramp |
| Reefer ship | Refrigerated cargo, mostly fruit before reefer containers took over | Smaller, boxy, now increasingly rare outside banana trades |
Shipping itself treats tankers as a separate category from \”dry cargo,\” though, with their own dedicated tracking considerations. The industry’s own lines are a little blurrier than the dictionary definition, and a tanker showing up in a \”types of cargo ship\” search is simply someone else drawing the category wider than shipping normally does.
How Big Do Cargo Ships Get?
Container ships hold the size records. The largest carry over 24,000 TEU (twenty-foot container units), more than a freight train several kilometres long, and stretch nearly 400 metres.
Bulk carriers are smaller but still huge. The biggest ore carriers exceed 360 metres and haul over 300,000 tonnes of iron ore, serving only a few routes between ports that can handle them.
A small general cargo ship may be under 100 metres and carry just a few thousand tonnes. Ship size depends on the cargo and the route, not on any universal standard.
Size also decides which ports a ship can enter. Only a few dozen ports have the deep channels, long berths, and tall cranes the biggest ships need. So giants stay on mega-hub routes, while mid-sized ships feed smaller ports into that network.
How Fast Do Cargo Ships Actually Travel?
Slower than most people guess.
A large container ship cruises at somewhere between 16 and 22 knots in normal service, which is roughly 30 to 40 km/h, and plenty of lines deliberately run slower than that to cut fuel burn, a practice the industry calls slow steaming. Bulk carriers and tankers are usually gentler still, often in the 12 to 15 knot range, because the cargo is not time-sensitive the way a retailer’s container booking can be.
None of that is fast by road or rail standards, and it does not need to be. A ship moving at 18 knots for three weeks still crosses an ocean. The economics of carrying tens of thousands of tonnes at once make up for the unhurried pace many times over.
Who Actually Operates These Ships?
Container shipping is dominated by a few big lines, like MSC, Maersk, CMA CGM, and COSCO, which control most of the world’s container capacity. Many share ships and sailings through alliances, so a vessel may follow a route and schedule partly set by a partner.
Bulk and tanker shipping is far more fragmented, with thousands of owners, from large fleets to small companies with a single ship. Ships are often chartered voyage by voyage, so the operator can change with the next load.
That makes operator brand unreliable for tracking. A ship’s name, MMSI, or IMO number stays the same no matter who charters it.
What AIS Shows About a Cargo Ship, and What It Doesn't
Every cargo ship over 300 gross tonnes on an international voyage carries AIS, the Automatic Identification System, and broadcasts its position continuously. Coastal receivers and satellites pick up the signal and a live map such as MarineRadar’s vessel tracking plots it. A single broadcast typically includes:
- Ship name, MMSI and IMO numbers
- Current position, speed and course
- Declared destination and estimated arrival
You can watch a specific ship’s position update every few minutes, see how its course has shifted, and get a rough ETA at its next port.
What AIS cannot tell you is anything about what is actually inside the ship. The protocol was designed to prevent collisions, not to describe cargo, so there is no field for container contents, no manifest, and no link between an individual box and the ship carrying it. A ship tracker can show exactly where a container ship is. It cannot say whether your specific parcel is aboard it, because that information lives in the carrier’s own booking and customs systems, not in the AIS stream. A closer look at how ship tracking apps actually receive this data makes the boundary clearer: position comes from satellite and coastal receivers in real time, cargo manifests never enter that signal at all. A search for a tracking or booking number returns nothing on a live map for the same reason. That number was never broadcast anywhere to begin with.
How to Track a Cargo Ship Live
Here is how to find and follow a specific cargo ship, step by step.
Step 1: Open a Live Ship Tracker
Go to MarineRadar on the web or in the app. The map loads with ships shown as icons across the world’s oceans and ports, each icon’s heading pointed in the direction the vessel is actually moving.
Step 2: Search for the Cargo Ship by Name or Number
Type the ship’s name, IMO number, or MMSI number into the search bar. The IMO number is the more reliable of the two if you have it, since it stays with a ship for its entire working life, while a name can be repainted after a sale. The map will centre on the vessel’s current position as soon as it matches.
Step 3: Filter by Vessel Type if You’re Browsing
If you don’t have a specific ship in mind and just want to see cargo traffic near a coastline or port, use the vessel type filter to show only cargo ships, or narrow further to container ships or bulk carriers. This cuts out the fishing boats, tugs, and pleasure craft cluttering a busy harbour view.
Step 4: Open the Vessel’s Detail Panel
Tap or click the ship’s icon and a panel opens with its speed, course, destination, and estimated time of arrival, along with the ship’s dimensions and type. This is the same information the ship itself is broadcasting, read straight off the AIS feed rather than summarised from a schedule.
Step 5: Follow the Route as It Updates
Leave the vessel selected and its position will keep refreshing as new AIS reports arrive, typically every few minutes for a ship underway. Over a few hours you can watch it approach a port, slow down for a pilot boarding, or divert around weather, which is a much clearer picture than a single static position ever gives.
Reading a Cargo Ship's Route and ETA
A ship’s displayed ETA is a projection, not a promise. It is calculated from current speed and the distance remaining to the declared destination. It shifts every time the ship speeds up, slows down, or changes course, and it says nothing about queueing time once the ship reaches a congested port.
For a container ship, planning a route in advance makes those swings easier to read. You can compare the ship’s actual track against the shortest theoretical path and see exactly where it diverged, whether that is a weather system, a canal transit, or routine traffic separation near a busy strait.
Watching a single vessel is one view. Tracking a container ship through a full voyage, load port to discharge, shows the same information in a more connected way. Worth doing once, if only to see what an AIS trail actually captures over weeks rather than hours.
Life and Work Aboard a Cargo Ship
A typical cargo ship runs on a small crew of just 20 to 25 people, working shifts around the clock. Contracts last four to nine months at sea, which is why crew welfare has become a visible issue in shipping.
Paying to travel on one is a real but niche option. A few freighter lines sell a handful of passenger berths, offering slow travel and a close look at how the ship works. It is not a cruise in price or comfort, and availability is limited, but freighter travel agencies still book it.
FAQs
What is a cargo ship called?
Cargo ship, freighter, and merchant vessel all describe the same thing.
What are the different types of cargo ships?
Five types cover most of the fleet: container ships, bulk carriers, general cargo or break-bulk ships, Ro-Ro vessels for wheeled cargo, and reefer ships for refrigerated goods. Tankers are sometimes counted as a sixth, depending on how broadly the question is framed and who is answering it.
What is the largest cargo ship in the world?
The record sits among a small group of ultra-large container ships, currently clustered around 24,000 TEU and close to 400 metres long.
Can you track a cargo ship in real time?
Yes. Any cargo ship over 300 gross tonnes broadcasts AIS continuously, and a live map such as MarineRadar plots its position, speed, course and destination as the signal updates, usually every few minutes while the ship is underway and less often once it is berthed.
Are cargo ships armed now?
Most are not; a minority crossing high-risk waters carry private security for that transit only.
Can you pay to travel on a cargo ship?
On a small number of freighter lines, yes, booked through dedicated freighter-travel agencies rather than a normal cruise or ferry operator. Berths are limited, schedules move with the cargo rather than a fixed itinerary, and most cargo ships carry no passengers at all.
How fast do cargo ships go?
Usually 12 to 22 knots, and often slower by choice to save fuel.
Track the ships behind the story
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