This tool is an area calculator designed to help you determine the exact size of your garden. You use this calculator to measure the total surface area of any garden bed, regardless of its shape. Knowing your garden’s square footage is the essential first step for any successful gardening project. For instance, it allows you to accurately determine how much soil, mulch, compost, or fertilizer you need to purchase. Furthermore, it helps you plan your plant spacing correctly to avoid overcrowding. This prevents you from buying too much or too little material, which saves you both time and money.
formula
1. For Square or Rectangular Gardens
This is the most common shape for garden beds.
Formula
Area = Length x Width
2. For Circular or Semi-Circular Gardens
a) Full Circle Garden
Formula
Area = 3.14159 x (Radius x Radius)
Supporting Calculation for Radius: The radius is half of the garden’s full width (diameter).
Radius = Diameter / 2
b) Semi-Circle Garden (Half-Circle)
Formula
Area = (3.14159 x (Radius x Radius)) / 2
3. For Triangular Gardens
This is common for corner garden beds.
Formula
Area = (Base x Height) / 2
Explanation of Variables:
Base: The length of one side of the triangle.
Height: The distance from the base to the opposite corner, measured at a 90-degree angle from the base.
4. For L-Shaped or Complex Gardens
The standard method for irregularly shaped gardens is to break the area down into smaller, regular shapes (like multiple rectangles or squares), calculate the area of each smaller shape individually, and then add them together.
Formula
Total Area = Area of Section 1 + Area of Section 2 + Area of any additional sections
Workflow
Divide the complex garden shape into a set of simple squares and/or rectangles.
Measure the Length and Width of each individual section.
Calculate the area of each section using the “Area = Length x Width” formula.
Sum the areas of all the individual sections to get the total garden square footage.
Soil and Mulch Coverage Guide
After you calculate your garden’s square footage, this table helps you estimate how many bags of soil or mulch you will need. Coverage can vary slightly by brand, so always check the product label.
| Material Bag Size | Desired Depth | Approximate Coverage Area |
| 1 cubic foot | 1 inch | 12 square feet |
| 1 cubic foot | 2 inches | 6 square feet |
| 1 cubic foot | 3 inches | 4 square feet |
| 2 cubic feet | 2 inches | 12 square feet |
| 2 cubic feet | 3 inches | 8 square feet |
| 2 cubic feet | 4 inches | 6 square feet |
| 3 cubic feet | 2 inches | 18 square feet |
| 3 cubic feet | 3 inches | 12 square feet |
Example
Let’s calculate the square footage of an L-shaped garden bed. This shape is best measured by dividing it into two separate rectangles.
Scenario:
- You have an L-shaped garden. You visualize it as a larger main rectangle and a smaller side rectangle.
- Rectangle A (the main part) has a Length of 12 feet and a Width of 5 feet.
- Rectangle B (the side part) has a Length of 6 feet and a Width of 4 feet.
Calculation Steps:
- First, we calculate the area of Rectangle A.
- Area A = Length x Width
- Area A = 12 ft x 5 ft = 60 square feet
- Next, we calculate the area of Rectangle B.
- Area B = Length x Width
- Area B = 6 ft x 4 ft = 24 square feet
- Finally, we add the areas of the two rectangles together to get the total square footage of the garden.
- Total Area = Area of Rectangle A + Area of Rectangle B
- Total Area = 60 sq ft + 24 sq ft = 84 square feet
The total area of your L-shaped garden is 84 square feet.
Most Common FAQs
To calculate the volume of material needed, you must multiply the square footage by your desired depth. First, you must convert the depth from inches to feet by dividing it by 12. The formula is: Volume in cubic feet = Area in square feet x (Depth in inches / 12). For example, if your garden is 84 square feet and you want a 3-inch layer of soil, the calculation is: 84 sq ft x (3 / 12) ft = 21 cubic feet of soil.
For gardens with irregular curves, the easiest approach is to approximate the area. You can do this by taking several width measurements along the length of the curve. Add these measurements together and then divide by the number of measurements you took to find an average width. Then, you can simply multiply the garden’s total length by this average width to get a close estimate of its square footage.
To measure the height of a triangular garden, first choose one side to be your base. Then, imagine a line that runs from the corner opposite your base to the base itself. This line must meet the base at a perfect 90-degree angle, like the corner of a square. The length of this specific line is the height. You can use a carpenter’s square to help you find the 90-degree angle to measure from.