Calculate retaining wall blocks, backfill gravel, drain pipe, and filter fabric quantities for your wall project.
Part of the Concrete & Masonry calculators — see all tools in this category.
Total length of the retaining wall
Exposed height of the wall
Standard concrete masonry unit
Recommended: 10% for cuts and breakage
Standard CMU (8x8x16) with 10% waste
5 courses x 15 per course
Top course cap stones
60 cu ft (1 ft behind wall)
4 in perforated pipe + outlet
Landscape fabric behind wall
Measure the total wall length in feet and the exposed wall height in feet. The height is the visible face of the wall from the base course to the top cap. Consider burying the first course partially for stability.
Choose from standard CMU (8x8x16), landscape blocks (12x4x12), or large landscape blocks (18x6x12). The block dimensions determine how many blocks per course and how many courses you need. Larger blocks mean fewer units but heavier individual pieces.
The calculator determines blocks per course (wall length / block length) and number of courses (wall height / block height). Wall blocks are calculated with a waste factor. Cap blocks for the top course are calculated separately.
Backfill gravel volume (1 ft depth behind wall), perforated drain pipe length (wall + 4 ft for outlet), and filter fabric area are automatically calculated. These accessories are essential for proper wall drainage and longevity.
The calculator alerts you about walls that may require permits (over 4 ft) or engineering design (over 6 ft). Long walls may need expansion joints. Always check local building codes before starting construction.
A compacted gravel base (4-6 inches deep) is critical for retaining wall stability. Excavate a trench wider than the block, add and compact crushed stone in 2-inch lifts, and check for level before laying the first course. The base course sets the alignment for the entire wall.
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