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Cargo & pallets

Cargo Lashing Calculator (CSS Code)

Check whether your lashings hold the cargo against sideways sliding, using the CSS Code rule of thumb and force balance.

Cargo

Results update as you type.
t
m/s²

Take it from a source suited to your ship, stowage position and mode.

Examples (illustrative)

Sea accelerations depend on the ship, the stowage position on board and the voyage conditions; 7.0 m/s² is only an example.

Friction

Lashings

pcs
How to enter the MSL
kN
°

Result

✓

Passes both checks

Needs at least 1 lashings per side (force balance) and 1 (rule of thumb)

Sliding force F = m·a70 kN
Resisting capacity93.36 kN✓
Cargo weight (m·g)98.1 kN
Σ MSL per side100 kN✓

Rule of thumb: Σ MSL per side ≥ weight

✓
Cargo weight (m·g)
98.1 kN
Σ MSL per side
1 × 100 = 100 kN
Lashings per side (rule of thumb)
1

Transverse force balance

✓
Sliding force F = m·a
10 × 7 = 70 kN
Friction μ·m·g
29.43 kN
CS = MSL ÷ 1.5
66.67 kN
f = μ·sin α + cos α
0.9589
Resistance of one lashing (CS·f)
63.93 kN
Resisting capacity
93.36 kN vs 70 kN
Lashings per side (balance)
1

Front view: lashings on both sides at angle α

α = 40°
10 tααF 70 kN
A simplified CSS Code Annex 13 check for education and early planning, not a calculation under the ship’s Cargo Securing Manual.

About this calculator

Cargo that is not properly secured can shift when a ship rolls, a truck brakes or a container is lifted. The result is not only damaged goods but burst container walls, a listing ship and danger to crew and port workers. Annex 13 of the IMO CSS Code (Code of Safe Practice for Cargo Stowage and Securing) gives a simple way to judge whether a securing arrangement is strong enough, based on the MSL (Maximum Securing Load), the safe working load of each lashing device.

This tool runs two simplified checks. First, the rule of thumb: the sum of the MSL of the lashings on each side should at least equal the weight of the cargo. Second, the transverse force balance: the force from acceleration (m·a) must be resisted by friction (μ·m·g) plus the lashings' contribution, Σ CS·f, where CS = MSL ÷ 1.5 and f = μ·sin α + cos α, with α the lashing angle to the deck. Common MSL factors are included for shackles, fibre rope, web lashings, wire rope, steel band and chain, together with typical friction coefficients such as 0.4 for timber on timber and 0.3 for steel on timber.

This is an educational simplification for early planning, not a calculation under the ship's Cargo Securing Manual. Design accelerations depend on the ship, the stowage position on board and the voyage conditions, so the value you enter must come from an appropriate source. For heavy or unusual cargo, involve a surveyor, the carrier or a cargo securing specialist.

Worked example

A 10 t machine sits on timber bearers on a steel deck (μ 0.3), transverse acceleration 7 m/s², one lashing per side with an MSL of 100 kN at 40°.

  • Weight: 10 × 9.81 = 98.1 kN; rule of thumb 1 × 100 kN ≥ 98.1 kN ✓
  • Transverse force: 10 × 7 = 70 kN; friction 0.3 × 98.1 = 29.43 kN
  • CS = 100 ÷ 1.5 = 66.67 kN; f = 0.3 · sin 40° + cos 40° = 0.959 → one lashing 63.93 kN
  • Capacity: 29.43 + 63.93 = 93.36 kN ≥ 70 kN ✓

One lashing per side passes both simplified checks.

How to use it

  1. Enter mass and acceleration

    Type the cargo mass in tonnes and the design transverse acceleration in m/s² from a source suited to your ship or mode.

  2. Choose friction and lashings

    Pick the surface friction coefficient, the MSL of one lashing (or derive it from breaking load and material), the angle α and lashings per side.

  3. Read both checks

    See the rule-of-thumb and force-balance results, the resisting capacity in kN and the number of lashings needed per side.

Frequently asked questions

What is MSL in lashing?
MSL (Maximum Securing Load) is the maximum load a securing device may take in service. The CSS Code derives it from the breaking load, for example 50% for web lashings and chain and 33% for fibre rope.
How many lashings do I need?
By the CSS Code rule of thumb, the MSL on each side should at least equal the cargo weight. A 10 t unit (98.1 kN) needs Σ MSL ≥ 98.1 kN per side, for example one lashing of 100 kN MSL.
Why does the lashing angle matter?
A steep lashing gives little sideways restraint. The factor f = μ·sin α + cos α drops as α increases, so steep lashings need more units.
What is the friction coefficient between steel and timber?
The CSS Code gives typical values of about 0.3 for steel on timber, 0.4 for timber on timber and 0.1 for dry steel on steel. Wet, oily or dirty surfaces can be far more slippery.
Is this result enough to approve cargo securing on a ship?
No. It is an educational simplification. Securing on board follows the ship's Cargo Securing Manual and the instructions of the carrier or surveyor.

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