How to Calculate Landscape Materials

Lay Out the Geometry

• 1

  Divide the area you want to landscape into basic geometric shapes, such as squares, circles, ovals, rectangles and triangles. Half- or quarter-circles and ovals are fine, too.

• 2

  Place a yard stake at each corner of each shape, and tie pieces of string from stake to stake until every shape is outlined. For circles, mark the four points that make the quarters of the circle and the center. For ovals, use the same method, but make sure to mark the middle of the longest distance across the oval's length and the shortest distance across its width.

• 3

  Measure the length of each string. Convert all measurements to feet, rather than feet and inches. For example, 3 inches equals .25 feet. Divide the number of inches by 12 to get the decimal equivalent.

• 4

  Write the measurement on a piece of masking tape with a permanent marker. Stick the tape on the string so you can refer back to the measurement.

Calculate Area and Volume

• 5

  Calculate the basic area for each of your rectangular or square shapes by multiplying the length by the height. This is the square footage for flat item measurements such as erosion cloth or seed coverage.

• 6

  Multiply the radius of your circular or semicircular areas by itself (e.g., a 4-foot-radius circle would be 4 times 4), and then multiply the result by 3.14. This is the square-foot area for a full circle. Divide the answer by two for half-circles or four for semicircles.

• 7

  Follow the circle formula for oval areas, but instead of multiplying one radius by its own value, measure the radius at the longest and shortest points of the oval and multiply these together.

• 8

  Multiply the base of each triangle area by its height, then divide by two for the triangle's square footage.

• 9

  Multiply the area of each shape by the depth of the landscaping material to get the cubic footage (volume) of the landscaping materials you need. Landscaping stone may be anywhere from 1 to 6 inches deep. Other materials generally fall within this range as well, so your figure for calculating the cubic feet should be between .083 and .5.