Conversion from 4 Square furlongs to Ares

Information about the Square furlong (sq fur)

The square furlong is a unit of area equal to ten acres, or 40,468.6 square metres. Its symbol is sq fur. A furlong is 220 yards, an eighth of a mile, so a square furlong is a hundred square chains and sixty-four of them make a square mile. It is one of the tidiest relationships in the imperial system and one of the least used.

The furlong is older than the acre and gave it its shape. The name means furrow long, and it was the distance an ox team was expected to plough before resting and turning. In the open fields of medieval England a furlong was a block of cultivated strips as well as a length, so the word described a place and a measurement at the same time, and the acre was defined as one furlong by one chain because that was what a day's ploughing produced.

That history explains why the square furlong is arithmetically neat but practically absent. Land was allotted in strips and acres, not in blocks a furlong on a side, so the square form never had a use even when the linear one was in daily service. A surveyor who needed ten acres wrote ten acres, and the square furlong was left as an entry in tables.

The length itself has survived by a peculiar route. Horse racing kept it, and races in Britain, Ireland, the United States, Australia and much of Asia are still described in furlongs: a six-furlong sprint, a mile and a half meaning twelve furlongs. Nothing else in modern life uses the unit, but racing uses it constantly, which keeps the word familiar to people who would struggle to say how long it is.

As an area it is a useful size to picture even so. Ten acres is a small farm, a large public park, about fourteen football pitches, or a city block of generous proportions. New York's Central Park covers roughly eighty-four square furlongs. The unit is large enough that anything measured in it is being described as a place rather than a property.

Converting is cleanest through the acre. Multiply by ten for acres, then by 0.4047 for hectares, or use the direct factor of 4.047 hectares to the square furlong. Going the other way, a hectare is about a quarter of a square furlong, which is close enough for rough comparison of old and new land records.

One square furlong equals 10 acres, 100 square chains, about 40,469 square metres, or about 4.047 hectares.

Information about the Are (a)

The are is a unit of area equal to one hundred square metres, written a. It is a square ten metres on a side. It was created by the French metric legislation of 1795 as the basic decimal unit of land, taking its name from the Latin word for a level open space, and it is the parent of the hectare that eventually overshadowed it.

The original scheme was tidy. The are would measure a garden or a plot, the hectare a field, and the centiare a single square metre, giving three decimal steps that covered everything from a doorway to a farm. In practice the middle rung carried almost all the weight: fields were described in hectares and buildings in square metres, and the are was left with the narrow band between.

It nevertheless survives in land registration, and there it is entirely alive. French, Belgian and Luxembourgish deeds record parcels as hectares, ares and centiares in three columns, so a plot might be written as 1 ha 25 a 30 ca, meaning 12,530 square metres. In Poland the ar is the ordinary way of describing a building plot, and in Indonesia and parts of central Europe it fills the same role.

For scale, one are is a square ten metres on a side: a generous garden, a small yard, or the footprint of a modest house with a little room to spare. A badminton court is a little over eight tenths of an are, a single-car garage about one fifth, and a tennis court about two and a half. It is the largest unit that still describes something a person can pace out in a few seconds.

In strict SI terms the are is exactly the square decametre, since a decametre is ten metres. The two are the same quantity written two ways, and the SI form is essentially never used, which makes the are one of the few cases where the older unit is the readable one.

Its main practical trap is the symbol. A single lower-case a is easily lost in running text or mistaken for an abbreviation, which is why deeds usually write it in a fixed column and why anything ambiguous is safer converted to square metres before it is passed on.

One are equals 100 square metres, 0.01 hectares, or about 1076.4 square feet.