English units of measurement
English units preceded Imperial and US customary systems.
English units of measurement developed from the systems used by the Anglo-Saxons and the ancient Romans. Prior to the Roman colonization of Britain, very little is recorded about local measurement practices. During the Roman period, Roman units were standard, but after the Anglo-Saxon era, a native foot of northern German origin became the basis for linear measures, with divisions into palms and thumbs. The rod was set at fifteen of these feet, and the acre was defined as a specific area of square rods. Roman units, however, persisted in construction and for the mile. A key early weight standard was the Saxon pound, established by King Offa, which linked a pound of silver to 240 silver pennies. A major redefinition occurred between 1266 and 1303 with the "Composition of Yards and Perches," which altered the yard, foot, inch, and barleycorn to smaller values but kept the old rod and acre, likely as a compromise between Anglo-Saxon and Roman systems. The Norman Conquest introduced only the bushel, with William the Conqueror confirming existing measures. The Magna Carta mandated standard measures for volume and weight without defining them. Two principal sets of standards later emerged: the Winchester Units, used from 1495 under Henry VII, and the Exchequer Standards, used from 1588 under Elizabeth I. These systems were replaced in England by the Imperial system in 1826, following an 1824 act that redefined many units. In the United States, independent before these reforms, English units were standardized as US Customary Units in 1832. The term "English units" can also ambiguously refer to these descendant systems.
- field
- Metrology
- nationality
- English
- known_for
- Predecessor to Imperial and US customary units
Lore & Background
English units of measurement evolved from Anglo-Saxon and ancient Roman units, used in England until 1826, when many were redefined or superseded by Imperial units. Their appearance varied over time, with two main sets: the Winchester Units (1495–1587) affirmed by King Henry VII, and the Exchequer Standards (1588–1825) defined by Queen Elizabeth I. The term "English units" is ambiguous, sometimes referring to the descendant Imperial system or United States customary units. Their range extended across England and the British Empire, later replaced by Imperial units in 1826 under a Weights and Measures Act of 1824, which retained many unit names but redefined standards. In the United States, independent before the 1824 reforms, English units were standardized as US Customary Units in 1832. Defining characteristics include a lineage from Anglo-Saxon and Roman roots: the Anglo-Saxon period used a North German foot of 13.2 inches, divided into 4 palms or 12 thumbs, with a cubit of 2 feet and an elne of 4 feet. The rod was 15 Anglo-Saxon feet, the furlong 10 rods, and an acre 4 rods by 40 rods (160 square rods). Roman units persisted in construction, and the Roman mile of 5,000 feet continued. From Offa of Mercia (8th century) until 1526, the Saxon pound (Tower pound) was the fundamental weight unit, based on Offa’s law dividing a pound of silver into 240 silver pennies. The Compositio of Yards and Perches (between 1266 and 1303) redefined the yard, foot, inch, and barleycorn to smaller values but retained the Anglo-Saxon rod and acre, possibly as a compromise between Anglo-Saxon and Roman systems. The Norman conquest introduced only the bushel, with William the Conqueror confirming existing Anglo-Saxon measures. Magna Carta (1215) stipulated standard measures for wine, ale, corn, and weight without defining them. Standards were renewed in 1496, 1588, and 1758; the last Imperial Standard Yard in bronze (1845) served until the yard was redefined internationally in 1959.
Reader's Guide
The legacy of English units persists in modern customary measurements in the United States and in historical references to pre-Imperial British measures. These units evolved from Anglo-Saxon and ancient Roman systems and were used in England until 1826, when many were redefined or superseded by Imperial units. Their application varied over time, by location, and for different purposes, with the term "English units" sometimes also referring to the later Imperial system or to United States customary units. The two principal sets were the Winchester Units, used from 1495 to 1587 under King Henry VII, and the Exchequer Standards, in use from 1588 to 1825 under Queen Elizabeth I. In England and the British Empire, the Imperial system replaced English units in 1826 following an 1824 Weights and Measures Act that retained many unit names but redefined and standardized definitions. In the United States, independent before the 1824 reforms, English units were standardized and adopted as US Customary Units in 1832. The system’s history includes a redefinition of the yard, foot, inch, and barleycorn by the "Composition of Yards and Perches" between 1266 and 1303, while retaining the Anglo-Saxon rod and acre. The Norman conquest introduced only the bushel, and the Magna Carta of 1215 mandated standard measures for volume and weight without defining them. Standards were renewed in 1496, 1588, and 1758, with the last Imperial Standard Yard in bronze made in 1845, serving until the 1959 international yard and pound agreement redefined the yard as 0.9144 metres. Over time, the system spread throughout the British Empire.
Did You Know?
- The term 'English units' can be ambiguous, sometimes referring to Imperial or US customary units.
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