What a stowage factor tells you
A stowage factor is the cubic space one tonne of a cargo occupies in a ship’s hold, including the small voids left between particles, expressed in cubic metres per tonne. It is, in effect, the reciprocal of the cargo’s stowed bulk density: a low stowage factor means a dense, heavy cargo, and a high stowage factor means a light, bulky one. It is the single number that decides whether a cargo loads the ship down to its marks by weight, or fills the holds by volume first.
The figures below follow the schedule values and group classifications in the IMO International Maritime Solid Bulk Cargoes (IMSBC) Code, the same source cited on each cargo page. They are typical ranges; the exact figure for a parcel depends on grade, moisture, and particle size, and is confirmed from the cargo declaration before loading.
| Cargo | Stowage factor (m3/t) | IMSBC group | Typically binds on |
|---|---|---|---|
| Iron ore | 0.30 to 0.50 | Group A | Weight (deadweight) |
| Aggregates | 0.50 to 0.70 | Group C | Weight (deadweight) |
| Bauxite | 0.65 to 0.85 | Group A or C | Weight (deadweight) |
| Cement | 0.65 to 0.75 | Group C | Weight (deadweight) |
| Clinker | 0.65 to 0.85 | Group C | Weight (deadweight) |
| Sulphur (formed) | 0.60 to 0.96 | Group C | Weight (deadweight) |
| Coal | 0.79 to 1.53 | Group B | Varies by grade |
| Salt | 0.89 to 1.11 | Group C | Either, near balance |
| Alumina | 0.93 to 1.11 | Group C | Either, near balance |
| Fertilizer | 0.80 to 1.40 | Group C (some MHB) | Varies by grade |
| Sugar | 1.10 to 1.30 | Group C | Volume (cubic) |
| Scrap metal | 0.70 to 1.50 | Group B or C | Varies by form |
| Petroleum coke | 1.25 to 1.67 | Group B | Volume (cubic) |
| Grain | 1.30 to 1.50 | Group C | Volume (cubic) |
| Wood pellets | 1.40 to 1.60 | Group B | Volume (cubic) |
Weight cargoes and volume cargoes
The stowage factor sorts cargoes into two practical camps. A dense cargo with a low stowage factor, such as iron ore at around 0.3 to 0.5 m3/t, loads the ship down to its load line with the holds part empty; the binding constraint is deadweight, and a large share of the cubic capacity goes unused. A light cargo with a high stowage factor, such as grain or wood pellets above 1.3 m3/t, fills the holds to the hatch coamings before the ship reaches its marks; the binding constraint is cubic capacity, and the ship sails with deadweight to spare.
A cargo near 1.0 m3/t sits close to the balance point where weight and volume run out together, which is the most efficient use of a hull. The stowage factor page works through the calculation, and the bulk carrier specifications guide explains grain and bale capacity, the cubic figures the stowage factor is compared against.
What the IMSBC group means for carriage
The IMSBC Code sorts solid bulk cargoes into three groups, and the group, not the stowage factor, drives the safety regime on board.
- Group A cargoes may liquefy if shipped above their transportable moisture limit. Iron ore fines and bauxite fines are the headline cases. The cargo must be certified below its moisture limit before loading, and a wet cargo can shift and capsize a ship.
- Group B cargoes possess a chemical hazard, such as self-heating, oxygen depletion, or flammable dust. Coal, petroleum coke, and wood pellets fall here, and each carries schedule-specific ventilation and monitoring requirements.
- Group C cargoes are neither liable to liquefy nor chemically hazardous. Most grains, cement, salt, and aggregates sit here, though they still bring practical issues such as dust, abrasion, or hold-cleanliness demands.
Because moisture and grade move a cargo between behaviours, the group and stowage factor for a specific parcel always come from the shipper’s cargo declaration and the IMSBC schedule, not from a generic table. For the cargoes themselves, see the dry bulk shipping hub; to match a cargo to a hull, the bulk carriers hub. When you have a parcel to move, tell us about your cargo and our desk will confirm the stowage and the right vessel.