About this calculator
Flat-top deck barges are the backbone of coal, nickel ore, sand and project cargo transport in Indonesia. Because they are almost box-shaped, capacity can be estimated quite well from length, beam, depth and maximum draft, with a block coefficient of about 0.88–0.95 depending on the length of the bow and stern rakes.
The calculator works out displacement = L × B × T × Cb × ρ, then DWT = displacement − lightship. When the empty weight is unknown it is estimated at 0.12 t per m³ of L × B × D (typical for steel barges; replace it with the yard figure when you have it). Less ballast, stores and equipment that stay on board, this becomes the cargo deadweight. The clear deck area is taken after edge margins for side boards and bollards, so you see the average deck load in t/m² and can compare it with the deck strength.
For bulk cargo, enter the side board or heap height and the stowage factor (coal about 1.2–1.4 m³/t, nickel ore about 0.5–0.7 m³/t). The calculator shows whether the barge is weight-limited or volume-limited, how many tonnes are realistic and the resulting draft. The actual draft limit follows the load line certificate and class approval; this calculation is for estimates and early planning.
Worked example
300 ft barge: 91.44 × 27.43 × 6.10 m, max draft 5.00 m, Cb 0.92, lightship 1,800 t, deductions 50 t, coal SF 1.25 m³/t heaped 4.0 m:
- Displacement = 91.44 × 27.43 × 5.00 × 0.92 × 1.025 = 11,826 t; DWT 10,026 t; cargo deadweight 9,976 t
- Clear deck (1 m margin) 89.44 × 25.43 = 2,274 m² → average load 4.39 t/m²
- Volume 2,274 × 4.0 = 9,098 m³ ÷ 1.25 = 7,278 t → volume-limited
- Draft with 7,278 t of coal: (1,800 + 50 + 7,278) ÷ 2,365 = 3.86 m (freeboard at max draft 1.10 m)
How to use it
Choose the barge size
Pick a 180–330 ft preset or enter your own length, beam, depth and maximum draft in metres.
Enter lightship and deductions
Enter the empty weight (or leave it estimated) plus ballast, stores and equipment that stay on board.
Enter deck data
Enter the deck edge margin and deck strength (t/m²) to check the average deck load.
Enter bulk cargo data
Enter the side board/heap height and stowage factor to see whether the cargo is weight- or volume-limited.