A bay plan is a set of cross-section drawings of a container ship, one per bay, showing where every container sits. Each position is written in the bay-row-tier system of ISO 9711-1: six digits such as 030482, meaning bay 03, row 04, tier 82. Once you know three simple rules (bays run from bow to stern, rows from the centreline outwards, tiers from the bottom up) you can find any container on the ship.

The bay-row-tier system in brief

Bay-row-tier is a three-dimensional address for every container slot.

Coordinate Direction Numbering rule
Bay Fore and aft (bow → stern) Odd 01, 03, 05… for 20' slots; even 02, 04, 06… for 40' boxes spanning two odd bays
Row Athwartships (centre → side) Odd 01, 03, 05… to starboard; even 02, 04, 06… to port; 00 on the centreline when rows are odd in number
Tier Vertical (bottom → top) Below deck 02, 04, 06…; on deck 82, 84, 86… (some ships start at 80)

Tier numbers are always even and go up by two for each layer. The jump between hold tiers and deck tiers makes it obvious at a glance whether a box is above or below deck.

Bays: from bow to stern

Bay 01 is the foremost bay. A 20 ft container occupies one odd bay. A 40 ft container occupies two adjacent odd bays and is recorded with the even number between them: bay 02 for 01 + 03, bay 06 for 05 + 07, and so on. If two 20' boxes are loaded in a 40' bay, each keeps its own odd bay number. The box sizes themselves are covered in our 40ft container dimensions guide.

Rows: from the centreline outwards

Rows are counted from the ship's centreline. Row 01 is the first row to starboard of the centreline, row 02 the first to port, row 03 the second to starboard, row 04 the second to port, and so on. On ships with an odd number of rows, the row exactly on the centreline is 00. Bay cross-sections are usually drawn as if looking from aft towards the bow, which puts starboard on the right of the drawing; confirm this in the bay plan legend.

Tiers: from the tank top to the deck

In the hold, the first layer above the tank top is tier 02, then 04, 06 and so on. On the hatch covers or deck, the first layer is tier 82, then 84, 86, 88. Some ships use 80 for the first deck layer; the vessel's own bay plan legend explains its numbering. Deck containers are secured with twistlocks and lashing bars, while hold containers are usually held by cell guides.

Worked example: decoding 030482 and 141086

Position 030482 → 03 | 04 | 82

  • Bay 03: odd, so a 20 ft slot. It is the second 20' bay from the bow (after 01).
  • Row 04: even, so on the port side. The port sequence is 02, 04, 06, so 04 is the second row out from the centreline.
  • Tier 82: the first tier on deck.
  • Result: a 20' container in bay 03, second row to port of the centreline, bottom deck tier.

Position 141086 → 14 | 10 | 86

  • Bay 14: even, so a 40 ft container occupying bays 13 and 15.
  • Row 10: even, port side. The sequence is 02, 04, 06, 08, 10, so this is the fifth row out from the centreline, fairly close to the ship's side.
  • Tier 86: the deck sequence is 82, 84, 86, so this is the third tier on deck.
  • Result: a 40' container in bay 14, fifth row to port of the centreline, third deck tier. Beneath it are two deck tiers (82 and 84) in the same row, holding either a 40' box or two 20' boxes in bays 13 and 15.

For comparison, 070106 → 07 | 01 | 06: a 20' container in bay 07, first row to starboard of the centreline, third tier in the hold.

Profile view and bay cross-sections

A full bay plan usually combines two kinds of drawing:

  • Profile (side) view: the whole ship from bow to stern with bay numbers along the top. It shows which bays sit forward of the bridge, aft of it and near the engine room, and which bays carry 20' or 40' boxes.
  • Bay cross-sections: grids of slots arranged by row (across) and tier (up), with the hatch cover line separating the hold section from the deck section.

The practical routine is to find the bay on the profile, open that bay's cross-section, then count rows from the centreline and tiers from the bottom. For shippers, being able to read positions helps when monitoring reefers, confirming that dangerous goods are stowed as declared, or helping a cargo surveyor trace damage.

Notation and colours on a bay plan

Each slot on a bay plan usually carries several pieces of information. Exact conventions vary by carrier and software, but you will commonly see:

  • Colour: often the port of discharge (POD), so planners can see the discharge sequence.
  • Container number: owner code and serial number per ISO 6346.
  • ISO type code: for example 22G1, 45G1, or 45R1 for a reefer.
  • Weight: the VGM in tonnes.
  • Special symbols: reefer marks, IMDG class for dangerous goods and out-of-gauge flags (over-height, over-width or over-length).

Alongside the drawings, the same data travels electronically in a BAPLIE message (an EDIFACT standard maintained by SMDG, with several versions in use, including 2.x and 3.x). The terminal at the next port uses the BAPLIE to plan discharge and loading. For the bigger picture, read what is a stowage plan.

Common mistakes

  • Assuming row 01 is to port. Odd rows are always to starboard.
  • Looking for a 40' box in an odd bay. 40' containers are recorded under even bays.
  • Reading tier 82 as the 82nd layer. It simply marks the first tier on deck.
  • Skipping the legend. Drawing orientation, colours and the first deck tier can differ between ships.
  • Misreading container numbers. Verify the check digit with the container number checker.

Try decoding the positions of your own containers from a booking or loading report, then match the container type with the ISO type code decoder. To arrange the goods inside a container before it gets its slot on the ship, use the Load Planner and make sure its weight is ready for the VGM. Bay plans and BAPLIE files are operational documents of carriers and terminals; Stowage.id does not replace the ship's plan, its loading computer or the chief officer's approval.