About this calculator
A bay plan is the cross-section of one container ship bay viewed from aft looking forward: columns are rows (00 on the centreline, odd numbers to starboard, even to port) and lines are tiers (02, 04 … in the hold; 82, 84 … on deck). Every slot holds one container with a weight and a POD (port of discharge). Planners stow it by three basic rules.
First, the stack weight must not exceed the allowed stack weight — the strength of the tank top or hatch cover and the lashings on deck. Second, POD order: boxes discharged first must be on top. When a box for the first port is buried under boxes for later ports, there is an overstow and a restow — expensive extra crane moves. Third, keep weight low where possible, so the VCG stays low and deck lashings are not overloaded, and keep the transverse moment balanced so the ship does not list.
This calculator simulates one bay: set the number of rows and tiers and the stack limit, then fill slots with a weight and POD sequence number. You get weight per stack, overstowed slots, heavy-on-light pairs, floating boxes, the cargo VCG and the port/starboard moment. The auto-stow button arranges a container list automatically: last POD at the bottom, heaviest first, alternating sides for balance. It is a concept exercise; real stowage also handles 20'/40', reefers, DG and whole-ship stability.
Worked example
Bay of 3 rows × 2 tiers, stack limit 60 t, five boxes: A (POD 1, 10 t), B (POD 1, 20 t), C (POD 2, 25 t), D (POD 2, 15 t), E (POD 3, 18 t). Auto-stow:
- Order: E, C, D, B, A (last POD first, then heaviest)
- Row 02 (port): D bottom, A top · row 00: E bottom, B top · row 01 (stbd): C
- No overstows; port 25 t = starboard 25 t → transverse moment 0
- Total 88 t, VCG (58 × 1.295 + 30 × 3.885) ÷ 88 = 2.18 m above the bay base; B (20 t) over E (18 t) flagged heavy on light
How to use it
Set the bay size
Choose the number of rows and tiers, the position (hold or deck) and the stack weight limit in tonnes.
Fill slots
Click a slot and enter its weight and POD sequence number (1 = first discharge port), or clear the slot.
Try auto-stow
Enter a container list (weight and POD) and press auto-stow for a balanced arrangement without overstows.
Check the warnings
Review overweight stacks, overstows, heavy on light, floating boxes, VCG and the port/starboard difference.