Conversion from 20 Decameters to Yards

Information about the Decameter (dam)

The decametre is ten metres, written dam. It is a valid SI unit formed with the prefix deca, but like the decimetre it is rarely used. The prefix deca is the only SI multiplier whose symbol is two letters, which makes it slightly awkward to write and may have contributed to its neglect.

Spelling varies. Decametre is the international form; dekameter appears in some American texts, and the symbol dkm is occasionally seen in older material, though dam is the form recognised by the BIPM. The similarity between dam and the abbreviation for decimetre has caused confusion, and some standards bodies discourage the unit for that reason alone.

Where it does appear, it is usually in surveying, forestry and agronomy. Field dimensions, plot spacing and tree heights sit conveniently in the range of a few decametres. Some European cadastral records use the unit. It also occurs in specifications for cable and hose supplied in ten-metre lengths.

The derived area unit is more familiar than the length unit. A square decametre is 100 square metres, which is exactly one are. The are is itself little used, but its hundredfold multiple, the hectare, is the standard measure of land area across most of the world. A hectare is 100 ares, or 10,000 square metres, and can equally be described as a square hectometre.

In practice most people express ten metres simply as ten metres, or as 0.01 kilometres when working at larger scales. The decametre is best understood as a formally correct unit that everyday usage has passed over.

The unit does appear in one everyday context without being named. Swimming pool lane lengths, running track segments and the spacing of street lighting are frequently set in multiples of ten metres. Planning documents that lay out plot frontages or building setbacks often work to the same grid. The quantity is useful; it is only the word that has fallen out of use.

Its square has fared better than the length itself. The are, a hundred square metres, is the square decametre under another name, and although the are is now rare its hundredfold the hectare governs land measurement across most of the world. The same pattern shows in the decare of a thousand square metres, which is the standard unit of farmland in Turkey, Greece, Norway and parts of the Balkans and is simply ten ares. So the decametre survives chiefly by inheritance: nobody quotes a field boundary in decametres, but a great deal of the world's land is bought and sold in units built from it.

One decametre equals 10 metres, 1000 centimetres, or 0.01 kilometres. It is about 32.8084 feet.

Information about the Yard (yd)

The yard is a unit of length equal to exactly 0.9144 metres, or three feet. The symbol is yd. It is the base unit of the imperial and United States customary length systems, with the foot and inch defined as fractions of it.

That relationship is the reverse of what most people assume. Since 1959 the yard has been defined against the metre, and the foot and inch follow from it, so every imperial length unit is ultimately derived from an SI definition. The International Yard and Pound Agreement fixed the value at 0.9144 metres exactly, reconciling small differences between the American and British yards that had persisted for decades.

The origin of the name is uncertain. Old English gierd meant a rod or measuring stick. The frequently repeated story that Henry I defined the yard as the distance from his nose to his outstretched thumb is not supported by contemporary evidence, though it has proved durable. A physical standard yard bar was maintained in London from 1760, and its destruction in the 1834 Palace of Westminster fire forced a lengthy reconstruction from surviving copies.

Sport keeps the unit prominent. An American football field is 100 yards between goal lines, and the game's vocabulary is built around yardage. Golf course distances are marked in yards in Britain and the United States. Cricket sets the distance between wickets at 22 yards, a figure inherited from the surveyor's chain.

Fabric and carpet are sold by the yard in the United States, and textile widths are quoted in inches alongside. Landscaping materials such as topsoil and gravel are sold by the cubic yard, which is 27 cubic feet or about 0.7646 cubic metres.

Its cube runs the construction trade in North America. Concrete is ordered, delivered and billed by the cubic yard, about 0.765 cubic metres, and a standard mixer truck carries eight or nine of them; excavation, gravel, topsoil and demolition waste are all quoted the same way. Golf keeps the linear unit just as firmly, with every hole on every scorecard measured in yards and every club sold on the distance it carries, so a player who reads a shot as a hundred and fifty yards is using a measurement the rest of the game's arithmetic depends on. Between them the two uses make the yard unlikely to disappear.

One yard equals 3 feet, 36 inches, or 0.9144 metres exactly. It is a little shorter than a metre, by about 8.4 centimetres.