Editing Ton (section)

==Units of volume==
{{See also|Tonnage}}
The [[Displacement (ship)|displacement]], essentially the weight, of a ship is traditionally expressed in [[long ton]]s.<ref>{{Cite web|last=DesVergers|first=Jake|title=Rules of the Road: Tricky tonnage measurement not about weight|url=https://www.the-triton.com/2017/10/rules-of-the-road-tricky-tonnage-measurement-not-about-weight/|access-date=2021-04-23|website=The Triton|language=en-US}}</ref> To simplify measurement it is determined by measuring the [[volume]], rather than weight, of water displaced, and calculating the weight from the volume and density.<ref>[https://books.google.com/books?id=vylCkqTg7H0C&pg=PA249 Displacement ton] Dictionary of international trade retrieved 22July2010</ref>
For practical purposes the '''displacement ton''' (DT) is a unit of volume, {{convert|35|cuft|sigfig=4}}, the approximate volume occupied by one ton of [[seawater]] (the actual volume varies with salinity and temperature).<ref>[http://www.oxfordreference.com/views/ENTRY.html?entry=t135.e351&srn=1&ssid=351170645#FIRSTHIT A Dictionary of Weights, Measures, and Units, Donald Fenna, 2002] {{ISBN|0-19-860522-6}}</ref> It is slightly less than the 224 imperial gallons (1.018&nbsp;m<sup>3</sup>) of the '''water ton''' (based on [[distilled water]]).

One '''[[Shipping ton|measurement ton]]''' or '''freight ton''' is equal to {{convert|40|cuft|sigfig=4}}, but historically it has had several different definitions. It is used to determine the amount of money to be charged in loading, unloading, or carrying different sorts of cargo. In general if a cargo is heavier than salt water, the actual weight is used. If it is lighter than salt water, e.g. feathers, freight is calculated in measurement tons of 40 cubic feet.<ref>{{cite web |url=http://www.msc.navy.mil/annualreport/2003/financial.htm |title=MSC 2003 in Review - Financial and Statistical Review |publisher=Msc.navy.mil |date=2003-09-30 |access-date=2010-07-31 |url-status=dead |archive-url=https://web.archive.org/web/20110722195701/http://www.msc.navy.mil/annualreport/2003/financial.htm |archive-date=2011-07-22 }}</ref><ref>{{cite web|url = https://www.ustranscom.mil/dbw/docs/FY18_Liner_Breakbulk_and_Container_Rates_and_Guidance.pdf|publisher = Military Surface Deployment and Distribution Command|title = Liner Ocean Transportation Program Stabilized Breakbulk/Dry Cargo and Container Billing Rates|date = 2018}}</ref><ref>{{cite web |url=http://bulk.resource.org/courts.gov/c/F2/182/182.F2d.916.235.21638.html |title=182 F.2d 916 |publisher=Bulk.resource.org |access-date=2010-07-31 |url-status=dead |archive-url=https://web.archive.org/web/20110727214911/http://bulk.resource.org/courts.gov/c/F2/182/182.F2d.916.235.21638.html |archive-date=2011-07-27 }}</ref><ref>{{cite web |url=http://www.stocktonport.com/TERMINAL%20TARIFF/POS%20DEFINITIONS%20GENERAL%20RULES%20AND%20REGULATIONS%20ttariffI.htm |title=Pos Ttariff General Definitions |publisher=Stocktonport.com |access-date=2010-07-31 |url-status=live |archive-url=https://web.archive.org/web/20110716144906/http://www.stocktonport.com/TERMINAL%20TARIFF/POS%20DEFINITIONS%20GENERAL%20RULES%20AND%20REGULATIONS%20ttariffI.htm |archive-date= 2011-07-16 }}</ref>

'''[[Gross tonnage]]''' and '''[[net tonnage]]''' are volumetric measures of the cargo-carrying capacity of a ship.

The '''Panama Canal/Universal Measurement System (PC/UMS)''' is based on [[net tonnage]], modified for Panama Canal billing purposes. PC/UMS is based on a mathematical formula to calculate a vessel's total volume; a '''PC/UMS net ton''' is equivalent to 100 cubic feet of capacity.<ref>[http://www.pancanal.com/eng/general/peajes-en-el-canal.html ''Panama Canal Tolls''] {{webarchive|url=https://web.archive.org/web/20080916113752/http://www.pancanal.com/eng/general/peajes-en-el-canal.html |date=2008-09-16 }}, [[Panama Canal Authority]]. Retrieved 10 May 2006.</ref>

The '''water ton''' is used chiefly in Great Britain, in statistics dealing with petroleum products, and is defined as {{convert|224|impgal|cuft m3|sigfig=4}},<ref>{{cite web|url=https://www.nist.gov/pml/wmd/pubs/upload/AppB-12-hb44-final.docx|title=NIST: Units and Systems of Measurement Their Origin, Development, and Present Status|website=nist.gov|access-date=1 May 2018|url-status=live|archive-url=https://web.archive.org/web/20160616205300/http://www.nist.gov/pml/wmd/pubs/upload/AppB-12-hb44-final.docx|archive-date=16 June 2016}}</ref> the volume occupied by {{convert|1|long ton|lb kg|0}} of water under the conditions that define the [[imperial units|imperial]] [[gallon]].