Conversion from Square leagues to Decares

Information about the Square league (sq lea)

The square league is a unit of area equal to nine square miles, or about 23.31 square kilometres. Its symbol is sq lea. A league here is three statute miles, 4828.032 metres, so a square league is a square three miles on a side and holds 5760 acres. It is an obsolete unit that survives in historical land records and in the names of places whose boundaries were drawn with it.

The league began as a measure of time as much as of distance. In Roman and medieval usage it was roughly the distance a person could walk in an hour, which meant that its length varied with the terrain, the country and the century. English practice eventually fixed it at three miles, but the French lieue, the Spanish legua and the Portuguese légua were all different, and none of them agreed with each other.

That variation matters for anyone reading old documents. A grant recorded in leagues cannot be converted safely without knowing which league the surveyor meant. Spanish colonial grants in Texas and California used the legua based on the vara, giving a league of about 4428 acres rather than 5760, and county boundaries in parts of Texas still follow lines that were laid out on that basis.

At sea the unit lasted longer than on land. The marine league of three nautical miles gave the old three-mile territorial limit its name, and charts and treaties used it into the nineteenth century. The modern territorial sea of twelve nautical miles replaced it, but the phrase survives in older law and in fiction, where a journey of twenty thousand leagues describes distance travelled and not depth reached.

As a plain quantity, a square league is a substantial piece of country: nine square miles is a large parish, a small city, or a block of farmland that would take an hour to walk across. It is the scale at which land stops being a holding and becomes a district, which is precisely why grants of that size were made to found settlements rather than farms.

For conversion, nine square miles, 23.31 square kilometres or 2331 hectares all describe the same area. Any figure taken from a historical source should be checked against the definition in use at the time, because the same word can differ by thirty per cent between two neighbouring jurisdictions.

One square league equals 9 square miles, 5760 acres, about 23.31 square kilometres, or about 2331 hectares.

Information about the Decare (daa)

The decare is a unit of area equal to ten ares, or one thousand square metres. Its symbol is daa. Ten decares make one hectare. Unlike the other members of the are family it is in daily commercial use, though under several different names, because it happened to match land measures that a number of countries were already using when they went metric.

Norway is the clearest case. The Norwegian mål was redefined as exactly one thousand square metres in the metrication of the late nineteenth century, and dekar has been the working unit of Norwegian farming and forestry ever since. Agricultural statistics, subsidy applications and farm sale advertisements are all written in dekar, and a typical Norwegian holding runs to a few hundred of them.

The eastern Mediterranean tells a similar story with different words. The Greek stremma became one thousand square metres on metrication in 1899, the Turkish dönüm was fixed at the same figure, and the metric dunam of Israel, Jordan and Iraq matches both. Bulgaria uses the decare directly, and its farm census is published in it. In each of these places a traditional unit of roughly this size was rounded to the metric value rather than abolished.

The reason it works is that a thousand square metres suits smallholdings. A hectare is a large field, and a hundred square metres is a garden; the decare falls between them, at about the size of an orchard plot, a vineyard parcel or a village building lot. It is also close to a quarter of an acre, which is why it reads naturally to people brought up with either system.

Reporting to international bodies converts it away. European Union agricultural returns, the statistics of the Food and Agriculture Organization and most academic work are all in hectares, so national figures in dekar or stremmata are divided by ten before they travel. This is a frequent source of order-of-magnitude errors in translated agricultural reporting, since a farm of 300 dekar is 30 hectares and not 300.

The symbol daa is awkward but unambiguous, being the deca prefix applied to the are. It should not be confused with da, which is the deciare and one hundred times smaller, nor with the prefix symbol da used before other units.

One decare equals 1000 square metres, 10 ares, 0.1 hectares, or about 0.247 acres.