Acreage Calculations

The Tool

• A measuring wheel looks like a rickety wheel mounted on the end of a stick. A thin driveshaft runs from the wheel to a counter higher on the handle that counts the number of revolutions of the wheel. The ratio of the gears in the counter translates the number of times the wheel turns into feet. You can use the measuring wheel to measure the length and width of the parcel of land as the first step toward calculating the acreage.

Making the Measurement

• When you use the measuring wheel to measure the land, try --- insofar as is possible --- to divide the parcel of land into easily measured geometric shapes; squares or rectangles are the simplest to work with, as you only have to measure two dimensions to arrive at the size of the area. Triangles can be quickly calculated if they are considered as half of a rectangle. Measure any two sides and, instead of length multiplied by width, the calculation becomes length multiplied by width divided by two.

An Acre, More or Less

• When you multiply the length of the land by the width of the land, you determine how many square feet the parcel contains. When you divide the result by 43,560, you immediately arrive at the size of the parcel, in acres. Parcels smaller than an acre, when divided by 43,560, give an answer in decimal form; for example, when the size of a parcel that's 21,780 square feet is divided by 43,560, the result --- 0.5, or 1/2 --- tells you what fractional part of an acre the parcel's size represents.

Calculating Acreage Using GIS

• A Geographic Information System is an interactive mapping system designed to display the Earth accurately. Using a GIS map as the basis for calculating acreage allows you to avoid "walking the ground." Most GIS programs even allow you to mark out a section of ground on the map by creating a polygon. You can then query the map to determine the acreage within the polygon you plotted.