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Retaining Wall Block Calculator

Blocks, caps and drainage gravel for a straight retaining wall.

How it's calculated

Blocks per course = wall length in inches ÷ block length, rounded up. Courses = height ÷ block height, plus the buried course (most makers want about 10% of wall height, at least one course, below grade). Drainage gravel assumes a 12-inch-wide zone behind the wall.

Example

A 30 ft wall, 24 inches high, in 12 × 4 block: 30 per course × 7 courses = 210 blocks plus 30 caps.

When to get an engineer

WallGuidance
Under 3 ft, no load aboveUsually DIY with maker's instructions
3–4 ftMany areas require a permit
Over 4 ft, or a slope, driveway or building aboveEngineered design usually required

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