Calculate exactly how many retaining wall blocks, caps, and base materials you need—no guesswork, no wasted trips to the store.
Ready to calculate
Enter your wall dimensions
per sq ft
12" ×
$3/block
per sq ft
12" ×
$4.5/block
per sq ft
18" ×
$6.5/block
per sq ft
18" ×
$8/block
Why expert review matters
Every calculator is reviewed by certified professionals to ensure accuracy.Sarah Kim's LA Degree, Drainage Cert certification ensures professional-grade precision.
How many blocks per square foot?
3 blocks for 12×4" size, 1.33 for 18×6" blocks
Do I need a permit?
Usually required for walls over 4 feet tall
How deep should the base be?
6" for walls under 3 ft, 8-12" for taller walls
Is drainage always needed?
Yes - 12" of gravel behind wall minimum
Enter your wall length and desired height, and the calculator multiplies these dimensions to determine total wall face area, then divides by your selected block size to calculate blocks needed. It automatically adds cap blocks (based on wall length), estimates base gravel for a proper foundation, and calculates drainage gravel assuming 12" of backfill depth. The final tally includes waste factor for cuts and breakage.
Formula
Blocks = (Wall Length × Wall Height) ÷ Block Face Area
Caps = Wall Length × (12 ÷ Block Length)
Base Gravel = Length × Width × Depth ÷ 27