You can calculate acreage by measuring a plot of land's length and width, multiplying those two figures together to find square footage, then dividing that number by 43,560. For irregular parcels, try splitting measurements into smaller rectangles or other geometric shapes, or use specialized software.
Acreage as a measurement is useful when buying and selling land, planning developments, or deciding how much seed or fertilizer would be necessary to utilize farmland fully. There are 43,560 square feet in 1 acre. A square-shaped acre measures 208.71 by 208.71 feet, a standard 40-acre parcel of land is 1320 feet by 1320 feet, and 1 square mile is 640 acres.
If you don't want to walk the land yourself or don't know its basic dimensions, you can hire a professional surveyor to measure acreage for you. Surveyors use geographical data and specialized tools to find a piece of land's acreage down to the most minute measurement possible, which is useful when buying and selling property.
For slightly coarser measurements, GPS devices and smartphone apps can also aid in your calculations. GPS units from Garmin and Magellan, among others, allows the user to calculate acreage simply by walking all the way around the perimeter of a plot of land while logging his steps. The software then calculates the square footage or acreage of the area that the user covered.