Retaining Wall Calculator
Calculate blocks, base gravel, drainage materials, geogrid reinforcement, and accessories for retaining wall construction. Supports standard, large, and Allan Block types with automatic geogrid calculations for walls over 3 feet.
Wall Dimensions
Walls over 3 ft require geogrid reinforcement
Block Type
Wall Options
Batter angle — 3/4" is standard for most blocks
Material Estimate
Number of Courses
9
rows of 4" blocks
Blocks per Course
20
12" blocks across 20 ft
Total Setback (Batter)
6.0"
0.75" x 8 courses
Blocks
Wall Blocks
199
incl. 10% waste
Cap Blocks
20
flat caps for top course
Construction Adhesive
9
tubes (28 oz)
Base & Drainage Materials
Base Gravel
0.74
cubic yards (6" deep x 24" wide trench)
Drainage Gravel
2.22
cubic yards (12" behind wall)
Total Gravel
2.96
cubic yards combined
Drainage
Perforated Drain Pipe
20
linear feet (4" perf pipe)
Filter Fabric
110
sq ft (non-woven geotextile)
Geogrid reinforcement is not required for walls 3 ft and under.
How to Use This Calculator
Enter the total wall length and desired wall height in feet. Select your block type — standard and Allan Block are 4 inches tall per course, while large blocks are 6 inches tall. Adjust the setback (batter) per course if different from the standard 3/4 inch. Toggle cap blocks on or off. The calculator automatically determines if geogrid reinforcement is needed (walls over 3 ft) and computes all base material, drainage, and accessory quantities.
Formula Used
Courses = Wall Height / Block Height. Blocks per Course = Wall Length / Block Length. Total Blocks = Courses x Blocks per Course x (1 + Waste%). Base Gravel (cu yd) = Length x 0.5 ft x 2 ft / 27. Drainage Gravel (cu yd) = Length x Height x 1 ft / 27. Geogrid Courses = Floor(Courses / 2) for walls > 3 ft. Adhesive Tubes = (Courses - 1) x Length / 20.
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Disclaimer
This calculator is for estimation purposes only. Results may vary based on local conditions, materials, and building codes. Always consult a licensed professional before making decisions based on these calculations. MyContractorTools is not responsible for any errors or omissions.