Panamax, Neopanamax, Suezmax — ship sizes explained

Most of the famous ship-size words are canal measurements wearing a ship costume. Panamax is simply the biggest ship that fits the Panama Canal's original 1914 locks: 289.56 metres long, 32.31 wide, 12.04 of draft. Neopanamax is the 2016 expansion locks: 366 by 51.25 by 15.2. Suezmax is the largest ship that can transit Suez fully laden — the canal has no locks, so the binding limits are 20.1 metres of draft and a beam-draft trade-off, with a 68-metre air draft under the Suez Canal Bridge.

Beyond the canals, the words keep the same logic with different chokepoints. Malaccamax is the Strait of Malacca's roughly 25-metre depth — the ceiling on the Asia–Europe route. Seawaymax is the St Lawrence Seaway's small locks: 225.6 by 23.77 metres, which is why Great Lakes ships look the way they do. Chinamax is not a waterway at all but a port standard — 360 by 65 by 24 metres, the largest dimensions China's ore terminals accept, and the envelope the Valemax fleet was designed to fill exactly.

These limits explain the shape of the world fleet better than any technology does. Container ships stopped growing at about 400 by 61.5 metres largely because of Suez and berth geometry; the half-million-tonne tankers of the 1970s died partly because they fit through nothing at all. Our Canal-Fit Checker runs any ship on this site against every one of these gauges and shows which dimension fails.