Retaining Wall Block Calculator

Count the blocks and courses for a segmental retaining wall.

Inputs
ft
in
Results update as you type — no submit
ResultsLIVE
Blocks to buy
80
20 per course
Courses
4
20 per course
Courses4 × 20 per course
Formula
blocks/course = 20 ft ÷ 12 = 20
total = 20 × 4 courses = 80
Diagram — wall elevationNTS
20 ft24″4 COURSES × 20WALL ELEVATION · RUNNING BOND
MeasureShedmeasureshed.com/calculator/retaining-wall-block-calculator
Retaining wall blocks — material listUNITS: FT/IN · SCALE: NTS
Inputs
Wall length20 ft
Wall height24″
Block size12 × 6 in
Cap courseNo
Results
Total blocks80
Courses4 × 20/course
Wall elevationNTS
20 ft24″4 COURSES × 20WALL ELEVATION · RUNNING BOND
Shopping list
☐ 80 × 12 × 6 in wall blocks
Formula
blocks/course = 20 ft ÷ 12 = 20
total = 20 × 4 courses = 80
Estimates for planning only — verify before purchaseSHEET 1 OF 1
How it works

A segmental retaining wall is built from identical blocks stacked in courses, so the count comes from two simple divisions. Blocks per course is the wall length divided by the block's face width, rounded up so the run is fully spanned. The number of courses is the wall height divided by the block height, again rounded up. Multiply the two and you have the wall blocks; add one more course of caps if you want a finished top.

A twelve-inch-wide block gives one block per foot of length per course, and a six-inch-high block gives two courses per foot of height — which is why the math lands on round numbers for common sizes. Change the block and the per-course and per-height counts change with it.

This tool counts blocks; it does not design the wall. Walls taller than about three feet, or any wall holding back a slope or a driveway, carry real load and usually need a permit, proper drainage, and often an engineer's sign-off. Keep DIY dry-stack walls low and check your local code first.

Worked example
Wall 20 ft long · 24″ high · 12 × 6 in block · no caps
blocks/course = 20 ft ÷ 1 ft = 20
courses = 24″ ÷ 6″ = 4 → total = 20 × 4 = 80 blocks
Questions from the yard
Divide the wall length by the block width for blocks per course, divide the height by the block height for the number of courses, and multiply. A 20 ft wall 24 in high in 12 × 6 in blocks needs 20 × 4 = 80 blocks.
Block counts for planning — walls over ~3 ft may need a permit or engineer
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