Tool Box

Pasture Acreage Calculator

It is important to be aware of the precise acreage of your individual pastures. This figure is extremely important in planning stocking rates, seeding rates, and fertilizer and herbicide applications. Over- or under-estimation of square footage will diminish results or waste input dollars. Calculating the acreage of your pasture is easily accomplished with the simple geometric formulas shown below. Match your pasture as closely as possible to one of the shapes below, then take the necessary measurements in feet. Large areas are best measured with the type of measuring wheel often used by surveyors. Input these measurements into our automatic pasture calculator to find your acreage.

Note: For irregularly shaped pastures, try to visually divide the area into a combination of the shapes below. Use the pasture calculator separately for each section, and on your own add the resulting acreages for your total.

Circle

Area = the radius squared multiplied by 3.146

Measure a straight line from the center of the pasture to any point on the fence.

 
Enter the radius r = ft
Your acreage is:

Rectangle

Area = length times width
Measure two adjacent sides of the pasture.
Enter the length of one side L = ft
Enter the height of one side W = ft
Your acreage is:

Square

Area = length squared

Measure one side of the pasture.

Enter the length of one side L = ft
Your acreage is:

Triangle

Area = base times height divided by two

Measure one side of the pasture for the base. Then measure a perpendicular line from the base to the opposite corner.

Enter the length of the base B =base
Enter the height H = Height
Your acreage is:

Oval

Area = short radius times long radius times 3.146

Measure SR from the center of the pasture to the fence in the shortest distance possible and LR from the center of the pasture to the fence in the longest distance possible.

For an area that looks like a half-circle or a half-oval, find what would be the area of the full shape and divide by two.
Enter the longest radius LR = ft
Enter the shortest radius SR = ft
Your acreage is:

Estimating Pasture Quality

A quick and accurate way to determine the percent ground cover of desirable plants in the pasture versus weeds or bare ground is to conduct an actual field count. This method, called the string intercept method, requires some measuring, some counting and some calculating, but it is more accurate than visual observation. At the same time you can conduct an inventory on the type of weeds or poisonous plants you have in the pasture.

What will you need?

  • A string, 30 feet in length, knotted or marked with a permanent marker at 6 inch intervals. The final string should have 50 knots or marks OR a 25 foot long tape measure
  • A clipboard or note pad
  • A pen or pencil

How do you start?

The knotted/marked string or tape measure is placed on the surface of the pasture, and pulled taut so there is no slack in the string or tape. Write on paper the following four headings:

  • bare soil
  • good grass or clover
  • weeds
  • name of weed

Then walk along the measure, and look to see what falls under each knot or mark, or at each ½ foot and 1 foot mark on the tape, and record what you find.

  • If there is bare ground, put one X or tick under that heading, then go to the next knot, mark, or 6 inch interval and record what you find under that mark.
  • Continue to take the counts, marking under the correct heading what you find under the knot, mark or interval on the tape measure.When finished, do the same thing again in a different area in the pasture.
  • Following an X formation usually provides a reasonable representation of the pasture, or lift one end of the string or tape, pivot it around and start another count.

When you finish you will have 100 X’s or marks on your paper. Total each number of marks. Because you have 100 counts total, that number under each heading will equal the actual percentage of bare soil, good grass or clover, and weeds in that area of the pasture. This information can be used in the questionnaire, or by you to help you determine:

  • if you should overseed or renovate the pasture
  • if you need to control weeds, and
  • if you identified the type of weed(s), determine the appropriate herbicide or any poisonous weeds to eradicate

  1. Rutgers
  2. Executive Dean of Agriculture and Natural Resources
  3. School of Environmental and Biological Sciences