What is the stowage factor of a standard 20ft container?

A 20ft general purpose container has a tare weight of ~2.2 MT, maximum payload of ~28 MT, and internal volume of ~33 m³. Its 'break-even' stowage factor is 33/28 ≈ 1.18 m³/MT — cargo with SF above this is volume-limited; below this is weight-limited. A 40ft standard container has ~67 m³ and ~28 MT payload, giving a break-even SF of about 2.39 m³/MT.

What is the difference between bale capacity and grain capacity?

Grain capacity is the total internal volume of a vessel hold measured to the inner surfaces of frames and beams — relevant for bulk liquids and fine granular cargo. Bale capacity is the usable volume measured to the inner surfaces of the cargo battens or ceiling — relevant for bagged or unitised cargo where packages cannot fill the spaces between frames. Bale capacity is typically 10–15% less than grain capacity.

How do I find the stowage factor for a commodity not in standard tables?

Measure the actual volume occupied by a sample weight, or request the SF from your supplier who may have loaded the commodity before. For packaged goods, calculate: (total volume of all packages including ullage) ÷ (net weight in MT). Shipping agents and P&I clubs publish SF tables for common bulk commodities.

Does stowage factor include packaging?

Yes — published stowage factors include the packaging (bags, bales, drums) and the ullage (unavoidable wasted space between packages). This is why bagged rice has a higher SF than bulk rice. When comparing SFs, make sure you are comparing the same packaging format.

Why does coal have a variable stowage factor?

Coal SF varies significantly by grade and origin: low-SF coking coal can be as dense as 0.7 m³/MT while high-volatility thermal coal can reach 1.0–1.1 m³/MT. Moisture content also affects density. Operators always request the specific SF from the shipper for each consignment rather than relying on generic tables.

How does stowage factor affect freight cost?

For bulk voyage charters, the freight rate is typically per metric ton. If a cargo has a high SF and fills the hold by volume before the maximum deadweight is reached, the owner loses revenue from unused weight capacity. Some charter parties address this with a 'full and complete cargo' clause or by specifying an expected SF and adjusting freight if it differs.

Stowage Factor Calculator

Is Your Cargo Weight-Limited or Volume-Limited?

Enter your cargo details or select a commodity to calculate the stowage factor, required volume, and how many containers or holds you need.

Commodity

Cargo weight (metric tons)

SF range: 1.4–2 m³/MT (using avg: 1.70)

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Commodity Reference

Stowage Factor Table by Commodity

Stowage factor (SF) is the volume in cubic metres (or cubic feet) occupied by one metric ton (or long ton) of a commodity. Higher SF = bulkier relative to weight.

Commodity SF (m³/MT) SF (ft³/LT) Limiting factor

Cotton (baled) 2.0–3.0 32–48 Volume

Tobacco (baled) 1.5–2.5 24–40 Volume

Rubber (natural) 1.3–1.8 21–29 Volume

Coffee (bagged) 1.5–2.0 24–32 Volume

Cocoa beans (bagged) 1.5–1.7 24–27 Volume

Timber / sawn lumber 1.5–2.5 24–40 Volume

Machinery (general) 1.5–3.0 24–48 Volume

Paper (rolls) 0.9–1.2 14–19 Borderline

Rice (bagged) 1.1–1.4 18–22 Borderline

Wheat (bulk) 1.2–1.4 19–22 Borderline

Sugar (raw bulk) 0.7–0.9 11–14 Weight

Coal 0.7–1.0 11–16 Weight

Steel coils 0.4–0.6 6–10 Weight

Iron ore 0.3–0.45 5–7 Weight

Copper (cathodes) 0.35–0.5 6–8 Weight

Aluminium ingots 0.5–0.7 8–11 Weight

Fertilizer (bagged) 0.9–1.2 14–19 Borderline

General cargo (mixed) 1.4–2.0 22–32 Volume

How It Works

Understanding Stowage Factor

Stowage factor is fundamental to freight planning, ship stability, and commercial cargo operations.

What stowage factor means

Stowage factor (SF) is the volume occupied by one unit of weight of a commodity — expressed as m³ per metric ton (metric) or cubic feet per long ton (imperial). A high SF means the cargo is bulky relative to its weight. A low SF means it is dense. The SF determines whether a container or vessel hold will be full by weight or by volume.

Weight-limited vs volume-limited

A standard 20ft container can hold approximately 28 MT and 33 m³. If your cargo has SF = 33/28 ≈ 1.18 m³/MT, it perfectly fills the container by both weight and volume. If SF > 1.18, the container fills by volume before reaching the weight limit (volume-limited). If SF < 1.18, it fills by weight before running out of space (weight-limited).

Voyage planning and freight rates

Ship operators use stowage factors to plan cargo intake and estimate how much of a vessel's capacity (deadweight vs bale capacity) a cargo will use. For bulk carriers, knowing the SF of a commodity determines how many holds are needed and whether the vessel is trading on weight or volume. Freight rates for bulk cargo often reflect this: light, bulky cargoes pay on volume; heavy, dense cargoes pay on weight.

Container planning

For containerised cargo, SF helps determine the optimal container type and quantity. Very low SF commodities (steel, copper) are weight-limited — you will hit the container's maximum payload before filling its volume. Very high SF commodities (cotton, tobacco) are volume-limited — the container is geometrically full while still well below the weight limit.

How SF is measured

Stowage factors are measured by loading a known weight of commodity into a calibrated hold and measuring the space it occupies, including ullage (unavoidable wasted space between packages, in corners, etc). Published SF values are averages — actual SF can vary with packaging, moisture content, and stowage method. For granular bulk cargo, compaction and trimming affect the actual figure.

IMSBC and bulk cargo risks

For bulk cargoes with low SF and high moisture (iron ore fines, coal, nickel ore), the International Maritime Solid Bulk Cargoes (IMSBC) Code requires testing for transportable moisture limit (TML) and liquefaction risk. Cargo that liquefies in the hold behaves like a liquid and can cause the vessel to capsize. Always verify moisture content against TML before loading.

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