A long ton is an imperial unit equal to 2240 pounds. This was a common measure of displacement in commonwealth nations (and by extension, formally the unit of international displacement measure) however it has generally been replaced with the metric tonne. The alternative short ton remains in use in the United States. In general, ton refers to short tons, however when used in relation to US naval ships, ton refers to long tons. The long ton should not be confused with the various forms of tonnage.