Definition
Avoirdupois weight is a system of weights historically used in English-speaking countries for measuring most ordinary commodities — including goods sold in bulk, meat, fish, and timber — as distinguished from troy weight (used for precious metals and gems) and apothecaries' weight (used for medicinal compounds). The avoirdupois system uses the pound as its base unit, with that pound divided into 16 ounces and further subdivided into drams and grains. Larger units — stone, quarter, hundredweight, and ton — build upward from the pound.
The system was the default commercial weight standard in English and American trade law. When a statute, contract, or commercial instrument specified a weight without identifying the system, courts and merchants generally presumed avoirdupois weight unless the subject matter (gold, silver, drugs) indicated otherwise.
Common Language
Modern common usage (Wiktionary): Avoirdupois refers to the system of weights based on a pound of 16 ounces, used for goods other than precious metals, gems, and drugs. In everyday speech, "avoirdupois" sometimes appears informally to mean body weight or heaviness generally.
Historical common usage (Webster's 1913): A system of weights by which coarser commodities are weighed, in which a pound contains 16 ounces or 7,000 grains. Distinguished from troy weight and apothecaries' weight.
The gap between common and legal usage is narrow but real. Ordinary speech uses "avoirdupois" loosely as a synonym for bulk or heaviness. In legal and commercial contexts, the term is precise: it identifies a specific, rule-governed system with defined unit relationships, and invoking it — or failing to invoke it — in a contract or statute determines exactly how much of a commodity changed hands.
Recognized Forms
/SUBTYPES
Bouvier's identifies three functional variants within the avoirdupois system, each calibrated to a specific trade:
1. General commercial avoirdupois — Used in almost all commercial transactions and common dealings. The standard scale: 60 grains = 1 dram; 8 drams = 1 ounce; 16 ounces = 1 pound; 25 or 28 pounds = 1 quarter; 4 quarters = 1 hundredweight; 20 hundredweight = 1 ton.
2. Meat and fish trade — A stone of 8 pounds is the operative unit, reflecting trade custom in those markets rather than the general commercial scale.
3. Wood and timber trade — Uses a clove of 7 pounds and a stone of 14 pounds (equal to 0.0014 hundredweight in the general scale). This diverges from the meat-trade stone and from general commercial practice.
These variants matter because the same word — "stone" or "quarter" — carried different numerical values depending on the commodity being weighed.
Why It Matters in Research
The primary research hazard with avoirdupois weight is unit instability across trade sectors. A researcher reading a historical contract, statute, or case involving a "stone" of goods cannot assume a fixed value without knowing whether the commodity was meat, timber, or something else. Bouvier's makes this explicit, and it is a known source of ambiguity in commercial disputes from the nineteenth century and earlier.
A second hazard is the quarter. Bouvier's records both 25-pound and 28-pound quarters within general commercial avoirdupois, reflecting real variation in English and American practice. Contracts specifying quantities in quarters — particularly in grain and dry goods trades — may be ambiguous on their face.
A third issue is the distinction between avoirdupois, troy, and apothecaries' systems. In legal instruments touching drugs, precious metals, or mixed commodities, the failure to specify which weight system applies was a recurring source of litigation. Historical cases involving pharmacists, assayers, and jewelers frequently turned on which system governed the transaction.
For corpus researchers working with nineteenth-century commercial law materials, statutes, or trade regulations, avoirdupois weight entries in legal dictionaries serve as a calibration point: they tell you what a jurisdiction's baseline assumptions were, and deviations from those assumptions in primary sources signal either specialized trade usage or potential dispute.
Historical Dictionary Support
Bouvier's is the sole source dictionary here, and its entry is functional rather than analytical — it provides the conversion tables for three trade variants without extended commentary on legal significance. This is characteristic of Bouvier's treatment of weights and measures generally: the entries serve as reference tables rather than doctrinal analysis.
What Bouvier's does not address is the legal consequence of using the wrong system or failing to specify a system in a contract. That question was resolved case by case, and researchers should not expect dictionary entries from this period to supply the answer. The dictionary establishes the technical standard; the caselaw establishes what happens when the standard is violated or ambiguous.
Bouvier's also does not note the gradual statutory standardization of avoirdupois weights in both English and American law across the nineteenth century, which progressively reduced (though did not eliminate) the variation between trade-sector customs and the general commercial scale.
Jurisdictional Note
The avoirdupois system was the operative commercial weight standard across common law jurisdictions, but unit values for subdivisions like the stone and quarter varied by trade custom and, in some periods, by locality. American statutory standardization generally followed English practice but was not always contemporaneous. Researchers working with pre-standardization materials should verify the applicable local or trade custom rather than assuming a uniform national standard.