Retaining Wall Block Calculator
Count the blocks for a garden retaining wall from its length and height and the face size of the block you picked, including the cap stones that finish the top.
Your results
Worked example
A garden wall is 6 m long and stands 0.6 m above ground, built with blocks that show a 40 cm by 20 cm face:
- Blocks per course: 6 m ÷ 0.40 m = 15 blocks
- Courses: 0.6 m ÷ 0.20 m = 3 courses
- Total blocks: 15 × 3 = 45 blocks
- Cap stones: one per block along the top = 15 caps
Standard practice is to bury the first course below grade for stability. If you bury one full course, add one more course of blocks: 15 more blocks, for 60 total, with the same 15 caps.
How this calculator works
Counts are based on the exposed face of the block, which is how wall block is sold and laid. Mortar and joint gaps are ignored because segmental wall blocks are dry-stacked. The calculator counts the wall as drawn; steps, corners, and curves all add cuts, so order a few spare blocks for breakage and trimming.
Common questions
How tall can I build before I need an engineer?
Most Canadian municipalities allow low garden walls up to about 1 m without a permit, but rules vary and any wall holding back a slope, driveway, or structure is a different case. Check your local bylaw before building, and keep this calculator to the block count, not the design.
Do I need gravel behind the wall?
Yes. A compacted gravel base under the first course and free-draining gravel backfill behind the wall keep water from pushing the wall over in freeze and thaw cycles. Those materials are separate from the block count shown here.
Estimates only. Results are provided for planning purposes and count blocks from face dimensions as stated on this page. This calculator does not design the wall: base depth, drainage, and height limits depend on your soil and local bylaws. Verify before building. Mississippi Maple accepts no liability for purchase or construction decisions made using this calculator.