Table of contents

Traditional English units

English units is a mix of influences from the different cultural invasions the islands have been affected by. A set of these units including the inch, yard, gallon and acre are part of the British (Imperial) system of measurements and have in modern times been standardized according to the metric system.

This article will take a look at the rest of the units not so often associated with the Imperial system but often related in ratios to Imperial units.

English length units

Relationship between English units of length
Short English units of length at the top followed by longer units with the respective ratios further down.

The variety of units used through English history is fascinating. There is coherence in the system but one must have a great memory and skills in mathematics to translate how many poppyseeds one fathom is. The graph shows the relationship between a set of older English units of length.

Real poppy seeds are in fact obtained from opium poppies which can have a medical effect. 40 grams of poppy seeds equals a medical dose of 10 mg morphine. Why this has been chosen as a units of length is in itself interesting, for our purposes however it is defined as a 1/4 of a barleycorn. The barleycorn is the base unit of UK and US shoe sizes.

Anatomic definitions

Done with the cereals, now consider the set of units based on the human body. In the image of the human hand, the unit inch is not included but is the length of a thumb. In English the word inch is derived from the Latin word uncia, meaning one-twelfth, of a foot. The distance labeled 1 is called a shaftment, meaning the palm plus an extended thumb. A hand is 4 inches and covers the palm and the width of the thumb labeled 2. Label 3 is a palm and equals 3 inches or 4 fingers. A span is the length between an extended thumb and the little finger indicated by label 4 equaling 9 inches. A finger or fingerbreadth is 7/8 inches and indicated by label 5. The slightly shorter digit is the distance labeled 6 and equals 3/4 inch.

Originally, the English foot was the same as the Roman foot equaling 296 mm. With the arrival of the Anglo-Saxons the North-German foot of 335 mm was introduced. The modern foot of 304.8 mm came in the late 13th century.

The distance from fingertips to the elbow is called a cubit and equals 18 inches. A unit commonly used for measuring cloth is the ell which equals the distance from from the fingertip of an outstretched arm to the shoulder of the opposite arm, a distance equaling 45 inch.

Stretch out both your arms and the distance between the fingertips is called a fathom equaling 6 feet.

Units of measurements based on the ratios of the human hand
Common derivation of the English length units defined by ratios of the human hand.

Agricultural definitions

A rod, which also is known as a perch or pole, is 16 1/2 feet. Is has been used when surveying land and in architecture. A chain equals four rods. The length comes from the chains used by surveyors when measuring distances used up until recent times. A Gunter's chain named after Edmund Gunter who was a 16th century English mathematician, was used when measuring distances used in geometric triangulation when charting. A gunter's chain equals 66 feet. A chain can be split into links where a link is a 100th of a chain or 7.92 inch.

A furlong is based on the distance a plough team could be driven without rest equaling 40 rods or 600 Anglo-Saxon feet, thus 660 modern feet. The old Roman mile was 5000 feet as of year 1066, but was extended to 5280 feet in 1592 to make it a whole number of furlongs (8). The modern mile is also called a statute mile. A league equals 3 miles. So a nautical league is different from a statute mile. Originally a league is the distance covered by an hours walk.

Miscellaneous units

A yard was originally the distance from the King's nose to his outstretched hand. The word yard is an old English word for staff, rod or stick. The stick used when measuring the anatomy of the monarch was then the standard yard throughout the kingdom. A yard is three feet and has is more recent times been defined by a standard bronze yard stick. See the article on the British Imperial system and the yard for more details.

The distance of one pace is originally a Roman unit deriving from the passus which was the distance from the heel of one foot to the the heel of the same foot when it touched the ground the next time.

Play with these units and try converting to meters or inch to see what they become in our contemporary units on the length unit conversion page.

English area units

English area units based on how much land different sets of ox teams can plough in a year.
English area units based on how much land different sets of ox teams can plough in a year. Image by Paul Lacroix.

The older English units for areas are closely connected to the agricultural life they evolved within. The acre is used in contemporary language but has very old history. It is from the beginning a Saxon unit meaning field. It was traditionally estimated as the area it was possible to plough in one day. It is more precisely defined as a rectangle with width of one chain (four rods) and the length of a furlong. Since furlongs vary between regions an English acre is 4,840 yd2, a Scottish 6,150 yd2 and an Irish 7.840 yd2.

A rood is a quarter of an acre or one furlong in width by one rod in length.

A carucate is the area a team of eight oxen can plough in one year, which would equal 120 acres. One eigth of that or 15 acres would be what a single ox may plow in a year and that is called a bovate. One the same topic, the area a pair of oxen may plough in a year (30 acres) is called virgate or yard land.

Finally, a perch is the area enclosed by one rod squared.

Convert between these and more modern units on the area conversion page.