Long ton (imperial ton)

Definition and practical equivalents

By definition the long ton is 2,240 pounds. In practical terms this corresponds roughly to:

• 2,240 lb (pounds)
• Approximately 1,016 kg (commonly rounded as 1.016 tonnes)
• About 35 cubic feet of seawater at a density of 64 lb/ft³, a relationship that made the unit useful for ship displacement calculations.

There are several other "ton" units that can cause confusion. The short ton (mostly used in the United States) equals 2,000 pounds, and the metric tonne is 1,000 kilograms (about 2,204.6 pounds). When precision matters, especially in engineering or international trade, it is important to specify which ton is being used.

History and maritime use

The long ton has its roots in older English weight systems and became formalized as part of the avoirdupois or imperial arrangements of measures. Its connection to a volume of seawater underlies its historical role in shipping: naval architects and authorities used long tons when reporting a ship's displacement and draught. Even in countries that adopted metric units, some maritime records and treaty language retained long tons for continuity. For example, interwar naval agreements and limits on capital ships were typically expressed in long tons for displacement.

Contemporary relevance and distinctions

Today the long ton survives in a few niche settings. It may appear when discussing older vessels, archived legal texts, or in countries that switched to metric units only recently. In the United States, the long ton may still be encountered in naval contexts when referring to ship displacement or historical descriptions of ships. International treaties governing naval construction historically used the long ton to describe limits on warships; similarly, descriptions of mid-20th-century battleships and cruisers frequently quoted displacement in long tons.

When reading measurements today, check the unit: if a value is given in "tons," it may mean long tons, short tons, or metric tonnes. Converting between them is straightforward once the unit is known, but the distinction matters in engineering, law, and historical scholarship. For clarity, write out the unit (for example, "long ton" or "tonne") or give both the conventional ton and the equivalent mass in kilograms.