Of all the traditions that are kept alive today the acre for land measurement has to be one of the daftest.
(Article by Phil Hall)
To begin with hardly anybody today really knows what an acre is let alone where it came from. Yet we see and hear it being quoted all the time in respect of land area both for housing and even industrial purposes.
So what is an acre? Well anyone could look it up in a table of conversions and find it listed as 4840 square yard, but why this peculiar number? Furthermore how come it isn’t a square number? (The square root of 4840 = 69.5701085 …)
It is in fact the area of a strip of land 1 chain wide by 1 furlong in length, where a chain is 22 yards and a furlong is 10 chains (hence 22 x 220 = 4840). According to popular history this is an estimate of how much land a farmer could till in a day with a horse drawn plough. Now that the reader knows this I’m sure it’s relevance to modern applications will become clear!
The proper metric unit of area is of course the square metre, but since it is rather small for land area of any size a unit known as the hectare has come into general use. It is quite simply a square 100 m by 100 m The name derives in fact from a contraction of the prefix hecto (x 100) applied to another metric unit of area known as the ‘are’ (prounced air) which is a square 10 m by 10 m This latter unit is rarely used nowadays.
The arithmetic is remarkably logical and simple. 100 square metres = 1 are, 100 are = 1 hectare, 100 hectare = 1 square kilometre.
With the demise of the ‘are’ the hectare is now better known as being 10 000 square metres.
The sadest thing of all about the retention of the acre is that it does nothing to help people understand the concept of area and how we measure it. Nothing could be more awkward than a rectangle 10 times as long as it is wide as means of guaging it even if that fact is known.
In truth it is more likely that when information about modern developments are quoted in acres it has actually been worked out in hectares and converted using the factor 1 hectare = 2.47 acre. A classic case of taking something easy and making it hard.