Garden Math: Calculating the Area and Depth of Your Garden - FineGardening (2024)

From fertilizer to mulch and paving stones to plants, too much of a good thing can mean, at best, unused material stored in the garage and, at worst, dead plants.

It can also mean that you have spent money you did not need to spend. On the flip side, finding that your paths look unkempt because you under­estimated how much mulch you needed can be discouraging, as can languishing plants—despite what you thought were carefully measured fertilizer applications. Whether you are a math wiz or have a math phobia, learning some simple calculations to use for common gardening situations can help you save time and money while you turn your garden into an Eden.

Learn more: 8 Ways to Save Money at the Garden Center

Here are some basic calculations that will help you figure out what you need.

Calculating the square footage of your garden

♦ Finding the square footage of a square or rectangular area of land

Multiply the length by the width to determine the square footage—or area—of a square or rectangle.

♦ Finding the square footage of a triangular area of land

• Consider the longest side of the triangle the base.
• Measure a perpendicular line from the opposite angle to the base to determine the triangle’s height.
• Multiply the base by the height, and divide that number in half to determine the area.

♦ Finding the square footage of a circular piece of land

• Find the center point of the circle.
• Measure from that point to the edge of the circle to determine the radius.
• Multiply the radius by itself.
• Multiply that number by pi (3.14) to find the area of your circle.

♦ Square footage of an irregular shape

• Break up the space into regular shapes (squares, rectangles, triangles, and circles).
• Determine the area of each shape.
• Add the areas of each shape to come up with an approximate area of the bed.

Finding the cubic footage of your garden

♦ To cover a level area

• If the thickness or depth of your material is measured in inches, convert it to feet.
• Determine the square footage of the space.
• Multiply the square footage by the desired depth of the material to determine the cubic footage—or volume.

♦ To level a sloped area

• Determine the length of the area you would like to level.
• Create a level line that extends out from the top of the slope and stops at a point directly above the bottom of the slope. This line represents the width of the area.
• Create a perpendicular line from the end of the width line to the bottom of the slope. This line represents the depth of the area.
• Multiply the length by the width by the depth to determine the cubic footage of the entire area.
• Divide that number in half (to account for the soil that is already there) to determine how much fill you will need.

Tip: Sometimes material sold in large quantities is measured in cubic yards. To convert cubic feet into cubic yards, divide the number of cubic feet by 27 (because there are 27 cubic feet in 1 cubic yard).

Patrick Beam plays with math on a daily basis for his professional landscaping business in Columbus, Ohio.

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