Panamax refers to the largest ship measurements that can pass through the original locks of the Panama Canal. The maximum allowable dimensions are 294.1 meters long, 32.3 meters wide, and 12 meters draft. Many cargo ships are designed to these exact maximum specifications. The Panama Canal is currently expanding to allow larger "Post-Panamax" ships to pass through new, wider locks.

1. Panamax
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The two ships seen here seem almost to be touching the walls of the Miraflores Locks.
Ships classified as Panamax are of the maximum dimensions that will fit through the
locks of the Panama Canal. This size is determined by the dimensions of the lock
chambers, and the depth of the water in the canal. Panamax is a significant factor in the
design of cargo ships, with many ships being built to exactly the maximum allowable
size.
Contents
[hide]
• 1 Dimensions
o 1.1 Exceptions
• 2 Impact on shipping
• 3 Expansion
o 3.1 Post-Panamax
o 3.2 Comparison of sizes
• 4 See also
• 5 References
[edit] Dimensions

2. Panamax is determined principally by the dimensions of the canal's lock chambers, each
of which is 33.53 metres (110 ft) wide by 320.0 metres (1050 ft) long, and 25.9 metres
(85 ft) deep. The usable length of each lock chamber is 304.8 metres (1000 ft). The
available water depth in the lock chambers varies, but the shallowest depth is at the south
sill of the Pedro Miguel Locks and is 12.55 metres (41.2 ft) at a Miraflores Lake level of
16.61 metres (54 feet 6 in). The height of the Bridge of the Americas at Balboa is the
limiting factor on a vessel's overall height.
USS Missouri, one of the Iowa class battleships, makes a very tight fit as she passes
through the Miraflores Locks of the Panama Canal in October 1945.
The maximum dimensions allowed for a ship transiting the canal are:[1]
• Length: 294.1 metres (965 ft)
• Beam (width): 32.3 metres (106 ft)
• Draft: 12.0 metres (39.5 ft) in tropical fresh water (the salinity and temperature of
water affect its density, and hence how deeply a ship will sit in the water)
• Height: 57.91 metres (190 ft) measured from the waterline to the vessel's highest
point
A Panamax cargo ship would typically have a displacement of around 65,000 tons.[2]
[edit] Exceptions
Vessels up to 62.5 metres (205 ft) in height may pass by prior approval, co-ordinated
with low tide at the Bridge of the Americas.
On an exceptional basis, vessels up to 32.61 metres (107 ft) in beam may be permitted to
transit, subject to additional draft constraints.

3. Vessels with structures extending beyond the maximum length and/or beam above the
level of the lock walls may be permitted transit subject to inspection and approval.
During an exceptionally dry season, when the water level in Lake Gatún is low, the
maximum permitted draft may be reduced.
The longest ship ever to transit was the San Juan Prospector, now Marcona Prospector,
an ore-bulk-oil carrier that is 296.57 metres (973 ft) long, with a beam of 32.3 metres
(106 ft).[3]
The widest ships to transit are the two North Carolina class battleships, USS
North Carolina and USS Washington, which have beams of 33.025 metres (108 ft
3.875 inches).[4]
[edit] Impact on shipping
An officer of the cruise ship Ryndam keeps a close eye on clearance while the ship is in
the lock. (The picture looks down the side of the ship to the top of the man's head, with
the wall of the lock at the top of the frame.)
Panamax continues to be a noteworthy factor in ship design, with an increasing number
of ships being built precisely to the Panamax limit, in order to transport the maximum
amount of cargo in a single vessel.
The increasing prevalence of vessels of the maximum size is a problem for the canal. A
Panamax ship is a tight fit that requires precise control of the vessel in the locks, possibly
resulting in longer lock time, and requiring that these ships be transited in daylight. Since
the largest ships cannot pass safely within the Gaillard Cut, the canal effectively operates
an alternating one-way system for these ships.
Many modern ships, known as post-Panamax ships, are far larger than this (and hence
cannot use the canal). This is the case for supertankers and the largest modern container
ships; much bulk merchandise such as grain products is moved primarily on Panamax (or
sub-Panamax) ships. U.S. Navy supercarriers are also in the post-Panamax class; the
Nimitz class aircraft carriers are 333 metres (1092 ft) long overall with a beam of
41 metres (134 ft), while the flight deck is 76.8 metres (252 ft) wide.
[edit] Expansion

4. Panamax container ship transiting the Panama canal. Note that some containers have
been offloaded and are transported by train over the isthmus to allow acceptable draft.
Panamax ship transiting the Panama canal. Note the hull's unique construction designed
to allow passage.
As early as the 1930s, new locks were proposed for the Panama Canal to ease congestion
and to allow larger ships to pass. On October 22, 2006 the Panama Canal expansion
project was approved by voters in Panama by a wide margin.
[edit] Post-Panamax
Post-Panamax or "over-panamax" is the term for ships larger than Panamax, which do
not fit in the original canal. On October 22, 2006 the ACP (Panama Canal Authority)
with the support of the Electoral Tribunal held a referendum for Panamanian citizens to
vote in favor or against the Panama Canal expansion. The Expansion was approved by
about 78% of the electorate. This project is expected to cost a monumental $5.3Billion
which are expected to be recovered within 11 years.
After expansion, the Panama Canal is expected to be able to handle vessels up to 12000
TEU in size; currently, it can only handle vessels up to about 5000 TEUs. It is estimated
that this expansion will be completed by 2014. A third set of locks, 427 meters (1,400
feet) long, 55 meters (180 feet) wide, with a draft of 18.3 meters (60 feet) will
supplement the two existing sets of locks.
[edit] Comparison of sizes

5. • class: Panamax => Panamax II
• Length: 1050 ft => 1400 ft
• Width: 110 ft => 180 ft
• Draft: 41 ft => 60 ft
• TEU: 5000 => 12000