The metric system of measurement uses the decimal system of 10 digits for counting, derived in ancient times from counting on one's fingers. If the North American colonies of Great Britain had instead been colonies of France at the time of the French revolution in 1789, this program on metric conversions would be no more necessary than a course on how to read Chaucer's "Canterbury Tales" in medieval English.

However, we have retained a quaint heritage of measuring length, weight and other quantities in the English "system" that is hardly a system at all. At least the process of converting from an English measurement to a metric quantity can follow a simple system that is the subject of this program.

Length: Traditionally, 1 inch was the width of a human thumb. By the end of the First Millenium in Anglo-Saxon England, the inch was defined as the length of 3 barleycorns. (The seed of barley grain was a base of measurements as far back as the Old Babylonian period in Mesopotamia (now part of Iraq), about 1800–1600 BC.) One foot was the length of 36 barleycorns; one yard was the length of 108 barleycorns. One mile was set at 40 furlongs by the English Parliament in 1592; 1 furlong was the traditional length of a furrow plowed by oxen on Saxon farms.

Weight: The English pound and ounce were defined as multiples of 1 grain, which was the weight of a single barleycorn.

Volume: The English gallon was originally the volume of 8 pounds of wheat (and thus also defined in terms of the barleycorn).