Definition
A unit of weight whose legal definition has varied by statute and context. Two principal standards appear in American and English legal sources:
1. Short ton: 2,000 pounds avoirdupois, as fixed by certain state statutes (including early New York law).
2. Long ton: 2,240 pounds avoirdupois, calculated as twenty hundredweights of 112 pounds each, as established under federal customs and revenue statutes.
A third standard, the metric ton (or tonne), equal to 1,000 kilograms (approximately 2,204.6 pounds), appears in modern regulatory and international trade law, though it is less frequently encountered in domestic common law contexts.
The critical point for legal purposes is that "ton" carries no single fixed meaning across all instruments. Its weight depends entirely on the governing statute, contract, or regulatory scheme.
Common Language
Modern common usage (Wiktionary): Any of various units of mass, originally notionally equal to the contents of a tun; principally the short ton of 2,000 pounds or the long ton of 2,240 pounds.
Historical common usage (Webster's 1913): Webster's 1913 unhelpfully lists "ton" only as a plural of "toe" (an archaic form), reflecting an editorial gap in that edition rather than actual common usage of the weight measure.
The gap between common and legal meaning is not one of kind but of precision. Ordinary usage treats "ton" as loosely interchangeable across its variants. Legal and commercial instruments cannot afford that ambiguity: a 240-pound discrepancy per ton compounds significantly across bulk commodity transactions, freight contracts, and customs calculations. Courts and drafters must pin the term to a specific statutory or contractual standard.
Common Confusion
Short ton vs. long ton: The two variants are numerically close enough that parties to contracts, freight bills, and commodity agreements sometimes use "ton" without specification, generating disputes when the governing jurisdiction defaults to one standard and the counterparty assumed the other. American commercial practice generally defaults to the short ton (2,000 lbs.); English and admiralty practice historically defaults to the long ton (2,240 lbs.). Researchers encountering unqualified "ton" in historical documents should determine the governing jurisdiction and applicable statute before assuming either standard.
Ton vs. tonnage: In admiralty and shipping law, "tonnage" is a distinct concept measuring a vessel's cargo-carrying capacity or displacement, not weight in the ordinary sense. The two terms share etymology but diverge sharply in legal application. See RELATED TERMS.
Why It Matters in Research
The dual statutory definition is the central research trap. Black's own entry flags the conflict directly: New York statute fixed the ton at 2,000 pounds; federal customs law fixed it at 2,240 pounds. A researcher reading a pre-twentieth-century contract, tariff schedule, or freight dispute must identify which statutory regime governed before interpreting any quantity term.
In the Law Mind corpus, "ton" appears most frequently in: (1) customs and revenue cases, where the federal long-ton standard applied; (2) commercial and commodity contracts, where state law and trade usage controlled; (3) mining and mineral lease disputes, where royalty calculations turned on which ton standard applied; and (4) admiralty freight and charter party litigation, where the long ton was standard but metric conventions increasingly appear in twentieth-century materials.
Modern regulatory materials—particularly environmental law (emissions calculations), energy law (coal and LNG contracts), and international trade—shift toward the metric ton. Researchers working across time periods should be alert to this transition, which is not cleanly marked in most sources.
Historical Dictionary Support
Both Black's editions are in agreement and are notably candid about the instability of the term: each acknowledges that the ton is "differently fixed, by different statutes" and identifies the two competing standards by citation to specific statutes. This is an unusual instance of a legal dictionary entry foregrounding definitional conflict rather than offering a single authoritative definition.
The first and second editions are substantively identical on this point; the second edition adds a parallel citation to the 1901 compilation of U.S. statutes (U.S. Comp. St. 1901, p. 1943), updating the reference without changing the substance.
What the historical dictionaries do not address: the metric ton, which had no significant American legal footprint at the time of either edition; the distinction between gross and net ton in railroad freight regulation; and the registered ton used in admiralty (which is a volume measure, not a weight measure at all). Researchers relying solely on Black's for this term will find the foundation adequate for nineteenth-century commercial disputes but incomplete for twentieth-century regulatory and admiralty contexts.
Jurisdictional Note
American domestic commercial law generally defaults to the short ton (2,000 lbs.) absent contrary specification. Federal customs statutes historically used the long ton (2,240 lbs.). Admiralty and international shipping practice follows the long ton or, in modern instruments, the metric ton. Jurisdictional identification is essential before any ton-based quantity can be interpreted.