Type your value in the appropriate box, then press the Return key or Tab or click outside the box, and enjoy the results! Finetune the output by setting thousands separator, adjusting the significance, the number of digits following the dot, or comma, if you wish.
Units of common measurement vary widely, from time to time, and place to place. Most units of measurement started as a reference to a physical object or concept. The foot was the length of a man's foot, the inch was the width of a man's thumb, an acre was the amount of land a man and two oxen could plow in a day, etc.
At first, most measurements were only approximations, but eventually many country's governments set each at a specific standard to make commerce possible and fair. Often, when people settled new lands, they used the names of old measurements, but set their own standards. Other times, similar sounding measurement names in different countries had greatly different values.
Some measurements were derived from other types of measurements, such as a barrel weight being the weight of a barrel of flour. Often, the same measurement had different values depending on the material being measured, such as a wine tun and a beer tun, or a hank of wool and a hank of cotton. These differences may seem odd today, but they made perfect sense to the people that used them.
A Frenchman first defined what he called the meter as one ten millionth of the distance from the North Pole to the equator along the Prime Meridian. It was later defined, in a more precise method, as the length of the path travelled by white light in vacuum during a time interval of 1/299.792.458 of a second.
The liter was originally defined as a cubic decimeter, and a kilogram was defined as a liter of pure water at a specified temperature. Later, the standard was changed such that a kilogram mass became the standard and the liter was derived as the volume of a kilogram of water. This has caused the liter to become slightly more than a cubic decimeter.
The International System of Standards (SI) was first proposed in France in the 17th century, but was not adopted by the authorities until 1795. The system defined that there was only one standard in each measurement type and each unit greater or less was a power of ten. This made conversions between units much simpler. During the 19th century, more and more countries made this system their standard, but notably not Great Britain or the United States of America. In 1965 Britain began changing to the metric system as a condition of membership in the European Common Market. The US government, recognizing the problems of international trade, officially made the metric system its standard in 1975, and is still getting used to it today.