How to Determine the Number of Acres in a Square or Rectangular Shaped Property

Multiply length x width then divide by 43,560 (number of square feet in one acre of land).

Example: If you have a rectangular property that is 660 feet wide by 1320 feet long, then you would multiply the length (1320 feet) times the width (660 feet) to calculate the total number of square feet in the property. Then to determine the amount of acreage, just divide that number by the number of square feet in an acre, which is 43,560. You get 20 acres in a property that is 660' x 1320'.

Here is the basic answer...

660 feet x 1320 feet = 871,200 square feet
871,200 square feet divided by 43,560 square feet = 20 acres

So, a property that is 660' x 1320' is 20 acres (see map below).
 

One Section of Land is 640 Acres - One Mile by One Mile (5280' x 5280')

Rectangular Survey System (Township and Range System)
Written land descriptions and legal descriptions may be based on the Rectangular Survey System, a metes and bound description or a coordinate description system. This system is based on the idea of parallels and meridians that circle the globe. The equator and all horizontal lines north and south of it are known as parallels. The vertical lines which converge at the north and south poles are known as meridians.
 

Legal Descriptions for a Section of Land

The Rectangular Survey System also has its own special meridians and parallels throughout the United States. The meridians are known as "principal" meridians (see figure 7 below). Each principal meridian has a parallel which goes with it. These are known as "base" lines. The points where these two meet are known as initial points. Some counties describe land using this system by referencing different meridians.

Township and Range System

County Assessor’s Property Identification System
Locating land is fundamental to the tax mapping process; therefore each parcel of land is given its own unique identifier. This is called the property identification number, assessor’s parcel number (APN), tax id, or parcel identification; it is known by different names depending on the county. A good identifier will permanently and distinctly locate one and only one individual parcel of land. In many jurisdictions, land is described by written descriptions or legally recorded plats.

Recorded Map Descriptions
Graphic land descriptions are based on the recording or filing of maps. These descriptions are known as "recorded map descriptions" or "legally recorded plats." Recorded map descriptions are descriptions of parcels by reference to lot numbers (or letters) and/or block numbers (or letters), and name or numerical designation given to a recorded or filed map.

Mapping and Photography
The County Assessor's office uses aerial photographs to locate and identify property. There are several types of aerial photography used as listed below:

• Aerial Photographic Enlargement is nothing more than a "blown-up" photograph. Neither tilt nor relief displacement are removed for these photographs. Because of this, you will not be able to make accurate measurements from the maps made from the photo. These photos are helpful for inventory of parcels and locating structures.
   
• Rectified Aerial Photograph is one in which distortions caused by tilt displacement have been removed. The rectification process is accomplished by projecting the photo image onto a flat surface that is tilted to eliminate the original tip and tilt of the aircraft. The objective is to project the image back to its correct shape and scale. Although relief displacement is not removed from rectified photographs, this type of photography provides acceptable accuracy for assessment mapping in areas of relatively flat terrain.
   
• Ortho-Photographs look a lot like the other two types of aerial photographs. However, it has the accuracy of a map drawn from ground survey information because tilt and relief displacement have been eliminated. Measurements of a land surveyor on the ground should "fit" when plotted on a true-to-scale ortho-photograph. Distances and area calculations on an ortho photograph are usually extremely accurate, and property lines will correspond closely to physical features.
   
• Digital Ortho-Photographs is an ortho photograph scanned or created in a digital format. These have the same accuracy as ortho photo sheets, but can be viewed and manipulated on the computer, with the capability to zoom in or out. This also provides us a method to lay property lines or any other data over the photo.