Retaining Wall Block Calculator

Find how many blocks, caps and tons of base and drain rock you need for a segmental block retaining wall.

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Blocks

Courses
Per course
Caps
Wall face
Base rock
Drain rock
Drain pipe
Cost

Wall List

Items you add are saved in this browser.

Wall	Size	Blocks	Caps	Rock Tons	Cost	Remove

How to Calculate Retaining Wall Blocks

Count courses (rows) and blocks per course. The exposed height sets the courses above grade, and the first course or more is buried for stability. Caps run the length of the top course.

Blocks per course = wall length (in) ÷ block length, rounded up

Courses = exposed height (in) ÷ block height, rounded up, + buried courses

Base rock = length × base width × base depth Drain rock = length × zone width × total wall height

Worked Example

Base, Embedment and Drainage

Allan Block's installation guide calls for a base trench 24 inches wide with at least 6 inches of compacted wall rock, a trench depth of 6 inches plus 1 inch for each foot of wall height (so the buried block depth is about 1 inch per foot of wall), and wall rock filling 12 inches behind the block. It calls for a drain pipe on gravity walls over 4 feet, reinforced walls and sites with poor drainage. Other block makers have similar details; follow the instructions for the block you buy.

Rock weights use about 2,800 lb per cubic yard (1.4 tons) for crushed wall rock.

Blocks per Square Foot of Wall Face

Face Size	Face Area	Blocks per Sq. Ft.	Per Foot of Wall per Course

Tips

Walls taller than about 4 feet, walls holding up a driveway, slope or building, and walls near a property line usually need a permit and an engineered design with geogrid. Many building codes require a design for walls retaining more than 4 feet of soil. Buy a few extra blocks from the same production run for cuts and color match.