Most gravel projects are not perfect rectangles. Driveways curve, patios have cutouts, and planting beds follow the yard. The simplest reliable method is to break the shape into pieces you can measure, then add the areas together.
Break the Area Into Simple Shapes
- Sketch the outline. Draw the driveway, patio, bed, or pad roughly on paper.
- Divide the sketch. Split it into rectangles, squares, and right triangles.
- Measure every piece. Write down length and width for rectangles, or base and height for triangles.
- Calculate each area. Rectangle area = length x width. Triangle area = base x height / 2.
- Add the pieces. The sum is the measured area to enter as square feet.
L-Shaped Area Example
Measure Slanted Edges as Triangles
If a section has a diagonal edge, do not measure the diagonal as the height. Measure the flat base and the straight height at a right angle, then divide by 2.
Use a Bounding Box for Fast Estimates
For a very organic bed, measure the longest length and widest width. Multiply them, then reduce the result if the shape leaves large empty corners. A common rough planning adjustment is 80 percent of the box area.
- Longest length x widest width = bounding box area.
- Bounding box area x 0.8 = quick irregular-area estimate.
- Use a higher percentage when the shape nearly fills the box.
- Add waste if the material will be hand-raked around curves.
Where the measurement goes
Measured area
Enter the final square footage after adding your smaller shapes.
US unit: sq ft. Metric unit: m2.Depth
Measure the planned finished material thickness.
US unit: inches. Metric unit: centimeters.Waste
Add extra material for curves, raking, spillage, and measuring uncertainty.
Use 5 to 10 percent for many landscape projects.