Question:
How do I determine the size of my garden bed or lawn in square feet?Answer:
Knowing the area of the garden bed or lawn is necessary for applying fertilizers or pesticides, determining how much mulch is needed, or determining the number of plants needed to fill a space.
The method for determining the area of your lawn or garden depends on the shape. Use the information below to find the area of your garden bed or lawn.
Rectangle | Triangle | Circle | Semicircle | Oval | Irregular-Shaped
Area of Rectangular Bed
A simple rectangular bed is one of the most straightforward bed shapes to determine the area. Simply, multiply its length by its width.
Area = length × width
Area of Triangular Bed
To determine the area of a triangular-shaped planting bed, measure the length of the base and then the height (the distance from the top point down to the base). Then, use the formula below to determine square footage.
Area = base × height × 0.5
Area of Circular Bed
For a round planting bed, multiply pi (π=3.14) by the radius squared. The radius equals the distance from the center of the circle to the edge.
Area = 3.14 × radius2
Area of a Semicircle Bed
For a semicircle (also called a half-moon or half-circle) bed, start by finding the length of the radius. For a semicircle, the radius equals the length of the flat/straight edge divided by two. Then, use the formula for the area of a circle and multiply it by one-half.
Area = 3.14 × radius2 × 0.5
Area of Oval (Elliptical) Bed
An oval bed (more accurately referred to as an ellipse) can be found after collecting two measurements. Measure from the center of the bed to the furthest edge point. This is called the major radius. Then, going back to the center, at a right angle to the major radius, measure from the center to the bed edge - this is the minor radius. Multiply those two numbers by pi (π=3.14) to get the area.
Area = 3.14 × major radius × minor radius
Area of an Irregular-Shaped Bed
Many garden beds have a more irregular shape. For beds comprising straight lines, simply break the bed apart into triangles, rectangles, and/or semicircles. Find the area of each piece and add them together.
For more complex irregular shapes, such as a bed shaped like a kidney bean, the bed area can be estimated with decent accuracy by first gathering several measurements. Find the length of the longest line within the shape - this is the length line. Along this length line, measure perpendicular width lines (at a 90° angle) to the length line. The distance between the width lines (called the segment width) must be equal. For example, you might measure the width of the bed every 3 feet along that length line. You can measure any number of width lines as long as they are equidistant from each other. The more width lines you measure, the more precise your area calculation will be. To find the area, add all of the width line lengths together and multiply that by the segment width.
Area = (sum of all width lines) × segment width
