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Acre and Hectare
Dec 02, 2021
Curiosity Corner By Dr. Jerry D. Wilson, Professor Emeritus of Physics Lander University
Question: What’s the difference between the acre and the metric hectare? (Asked by a curious column reader.)
Reply: Both are units of land area. The acre is the common unit in the United States and the United Kingdom (UK). The hectare is used in metric countries, as in Europe and the Middle East. We buy the farm in acres and they buy it in hectares. Our acre had its origin centuries ago. It began as the amount of land that could be plowed in a single day by a team of oxen. This area designated in units, called perches, was 40 perches long and 4 perches wide. Forty perches were roughly the distance a team of oxen could plow a furrow before having to rest, and was a "furrowlong,” which became a furlong (220 yards), a unit still used in horse racing. The perch was later called the rod. An acre was 40 rods long and 4 rods wide or 160 square rods. The 4rod width became the length of a surveyor's chain (another unit) and is the distance between wickets in cricket (sticky wicket).
The size of an acre has varied over the years because of the difference in length units. In the United States, the acre is currently based on the U.S. survey foot and is 4840 square yards.
In the metric system, the special name for the unit of land area is the "are,” which is 100 square meters (a square 10 meters on a side) or about 119.6 square yards. This is a relatively small area so the hectare (100 ares) is commonly used (hect is the metric prefix meaning 100, analogous to centi meaning 1/100). So, with all this, we have 1 hectare = 2.47 acres.
As you can see, the science of metrology (measurement) has a stormy history. This is primarily due to a lack of standardization because a lack of communications. In the old days, different regions adopted different standards; and as commerce developed, there were mixed units, for example, different lengths for the same unit. Now we have international committees that set standards so everyone measures the same for the same unit. Also, we are going metric with the International System of Units (SI), which is much easier because it is a decimal (base10) system.
I dare say that some of you may not be too enthused about the metric system, but it is easier because everything is based on multiples of 10. You are already familiar with a decimal (base10) system: our money.
$1 equals 10 dimes, 1 dime equals 10 cents, and 1 cent equals 10 mils (if you pay taxes). Or, another way of looking at it, a penny is a centidollar (1/100 of a dollar), a dime is a decidollar (1/10 of a dollar), and a mil is a millidollar (1/1000 of a dollar).
Try setting up a money system with a base12, similar to our base12 length measurements. 12 inches equals 1 foot. Let's see, 1 dime equals 12 cents...
That will help you go metric.
C.P.S. (Curious Postscript): “Having ten fingers and ten toes for counting, we are born to use the metric system.” Anonymous
Curious about something? Send your questions to Dr. Jerry D. Wilson, College of Science and Mathematics, Lander University, Greenwood, SC, 29649, or email jerry@curiositycorner.net. Selected questions will appear in the Curiosity Corner. For Curiosity Corner background, go to www.curiositycorner.net.






