How to Estimate Retaining Wall Materials
Building a retaining wall requires more than just blocks; proper planning for drainage is crucial to prevent the wall from collapsing under hydrostatic pressure. Here is how our calculator figures out your materials.
Calculating Wall Blocks
To determine how many blocks you need, you first calculate the square footage of the wall face (Length × Height). Next, you calculate the square footage of a single block by multiplying its length by its height (in inches) and dividing by 144. Dividing the total wall area by the block area gives you the net block count. We automatically add your selected waste percentage to account for cuts at the ends of the wall.
Capstones
Capstones finish the top of the wall. Because they are laid end-to-end along the length of the wall, their calculation is strictly linear. We convert the wall length to inches and divide by the length of the capstone.
Drainage Gravel (Backfill)
The most common cause of retaining wall failure is trapped water. Industry standards recommend at least 12 inches of clean, crushed gravel directly behind the wall for drainage. We calculate this volume (Wall Length × Wall Height × 1 foot wide) to give you the required cubic yards of backfill gravel to order.