Open Field: History of the Acre

Open Field: History of the Acre

If you’ve ever dealt with any type of real property, whether it’s undeveloped land, commercial space to set up a business, or residential property to buy your new home, then you’re familiar with the acre. Square feet and acres are the standard units of measurement we use to describe the size of real estate. But have you ever stopped to think about what an acre actually is, where it came from, why we use it, and why it’s the size it is?

Most people probably haven't, and you can’t blame them in the busy world we live in. They just accept that the acre is what we use to quantify land and move on to the next item on their checklist. Not only is it interesting, but it can be extremely beneficial to take time out of your busy schedule to contemplate the things we do and why we do them. Sometimes people continue to do things a certain way simply because that’s the way it's always been done, when there may be a much better option available if we’ll stop to take a look.

Where did the acre come from and why is it the size it is?

The word “acre” traces back to the Old English term æcer meaning “open field” and was generally used to describe unoccupied country. In English, it was historically spelled “aker” and was related to the Latin word “ager” meaning “field.”

The very first definition of an acre was very interesting. Originally, an acre was the typical area of land that could be plowed by one man, in one day, using a team of oxen and a wooden plow. If you’re thinking… that seems like an inexact science, you’d be right. Here’s the story explaining how you can come up with an acre measurement using that early way of doing things.

It was standard practice to rest the oxen after they plowed ⅛ of a mile (660 feet). A unit of measurement came out of this practice known as a furrow-long, or furlong which measured that exact distance of 660 feet. A farmer would want to plow as much and as far as he could before he had to rest the animals. The easiest way to accomplish this was to plow as far as he could in a straight line. Turning the plow around wasn’t as easy as it might sound with the oxen team in the heat of the sun. Farmers tended to plow long distances to reduce the number of times they’d have to turn the plow in the opposite direction as well.

Old Plow
Early Plow

Just how big is an actual acre?

Farmers took pride in being able to plow a straight furrow. With a plowshare around 10 inches wide, your average farmer supposedly could plow a furlong’s length 80 times in a day covering a width of around 66 feet. 66 feet multiplied by a furlong of 660 feet comes out to 43,560 square feet, the exact amount of land area we call an acre today.

As you can easily see, there are many variables in this equation. The chances of an actual farmer plowing exactly 43,560 square feet every time they stepped on the field were probably reasonably small. How old is the farmer and what kind of shape is he in? Are the oxen well fed and healthy or in bad condition, old, or sick? Is the field topography level with rich soil or is it hilly and rocky? These variations translated into variations in the area a farmer could till, which in turn resulted in variation in the size of an acre. During his reign in England from 1272 - 1307, Edward I (also known as Edward Longshanks) enacted a statutory value for the area of an acre as 4 rods wide by 40 rods long (one rod equals 16.5 feet). Edward III, Edward VIII, George IV, and then Queen Victoria in 1878 with the Weights and Measures Acts also contributed to creating exact values for the acre.

Why use the acre to measure the area of property?

There are all kinds of units of measurements we could use to measure land area, so why do we use the acre? There are several reasons. The acre is what England was using at the time the United States was being established. Since that’s what we’ve always used and often don’t like change, we’ve kept using it.

Large Acreage Property
Small Acreage Property

More importantly, the acre makes sense for all property sizes. There are times when square miles is used for large tracts of land, but it wouldn’t be practical to use square miles on small properties. A square mile is the equivalent of 640 acres. It’s much easier to envision half an acre than 1/1,280 of a square mile. Square feet is often used with residential and certain commercial properties, but when you start getting into larger sized real estate you’re going to be talking thousands and millions of square feet, which isn’t practical either. The acre works for large and small properties alike.

What about surface area? It makes sense to wonder if surface area comes into play in the measurement of acres. What about hilly or mountainous land as opposed to flat, level ground? The answer is surface area doesn’t matter in acreage. Surveyors use basic geometry (geometry literally means earth measurement) to calculate acreage based on a common horizontal topography called plane surveying for most all types of land. Even though a parcel may contain a significantly larger surface area than another, the surveyor will act as though they are both flat and they could both end up totaling the same acreage.

Converting acres to square feet and square feet to acres

Since square footage is used with so many properties, especially with structures on them, it’s useful to know how to convert square feet to acres and acres to square feet. The easiest way to do this is to use proportions or simple multiplication and division.

Acre To Sq Ft

When converting acres to square feet, since 1 acre = 43,560 square feet, multiply the acreage by 43,560. Here's a simple example.

0.85 acres is how many square feet?

0.85 x 43,560 = 37,026

0.85 acres is the same as 37,026 square feet.

When converting square feet to acres, simply divide the square footage by 43,560.

59,670 square feet is how many acres?

59,670 / 43,560 = 1.37

59,670 square feet is the same as 1.37 acres

Now that you know how to do the calculation manually, The Calculator Site provides a handy calculator that allows you to convert square feet to acres and acres to square feet. In this short video by America’s Heartland, Dan Macon sums up just how big an acre is and how many average bushels of certain crops are produced on an acre.

Take a look at these conversions. Some you may recognize and some you may not.

  • 1 acre = 43,560 square feet (66 x 660)
  • 1 acre = 4,840 square yards (22 x 220)
  • 1 acre = 10 square chains (1 x 10)
  • 1 acre = 4,047 square meters
  • 1 acre = 0.405 hectare
  • 1 acre = 160 square rods (4 x 40)
  • 1 acre = 160 perches
  • 1 acre (perfectly square) = 208.71 feet x 208.71 feet
  • 1 chain = 66 feet
  • 1 furlong = 10 chains = 660 feet
  • 1 rod = 16.5 feet = 5.5 yards
  • 1 chain = 4 rods
  • 1 hectare = 2.471 acres
  • 1 Megalithic Yard (MY) = 2.72 feet
  • 1 perch = 1 square rod
  • 1 perch = 0.00625 acres
  • 1 square mile = 640 acres
  • 1 mile = 80 chains = 8 furlongs = 5,280 feet = 1,760 yards
  • 1 football field (including end zones) = 1.3 acres
Furrowed Farm Land

The acre is interesting in that it can literally be any shape, as long as the total area of the shape is 43,560 square feet. Acreage comes into play in all sorts of outdoor endeavors whether it’s buying and selling property, hunting, or landscaping. Since everyone needs a home, most people deal with real estate in one way or another throughout their lives. When it comes to land, acres are especially important since the price you’re going to pay is largely dependent on its size. Hopefully knowing a little background and history will make dealing with acres a little more interesting to you in the future.


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