Retaining Wall Block & Backfill Calculator

Wall inputs

Wall & block

Block unit

Pick a common SRW block face or choose custom to set length and height by hand.

Wall length

Exposed wall height

Finished face above grade — courses are counted from this height.

Block face length

Block face height

Course pattern

Staggered (running bond) shifts alternate courses half a block — the standard look, needs a few cut blocks.

Cap & base

Cap course

Cap block length

Base-course gravel depth

Base gravel width past the wall

Crushed stone spreading past each face of the wall — stretch it for frost or soft ground.

Backfill & drainage

Drain-rock backfill depth behind wall

Clean 3/4″– drain rock between the blocks and the soil cut, over the full wall height.

Geotextile fabric

Unit costs

Block cost per unit

Cap block cost per unit

Base-course gravel cost

$/yd³

Drain-rock aggregate cost

$/yd³

Geotextile fabric cost

$/ft²

Plan & cost

Blocks per course

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Courses high

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Total blocks

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Caps

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Base gravel

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Drain backfill

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Fabric

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Material cost

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Item	Qty	Cost

Wall cross-section

Left: retained soil · center: wall blocks · right: drain rock · bottom: base-course gravel

Standard segmental retaining-wall rules

Base course: level crushed-stone base at least 6–8″ deep and wider than the wall; roughly double the width in frost climates.

Backfill: 12–24″ of clean drain rock behind the blocks, full wall height; walls above ~4 ft typically need engineered geogrid reinforcement.

Drainage: a perforated pipe at the base, and geotextile wrapped around the stone so fines don’t clog the voids.

Block fitting: course count rounds up from face height; staggered bonds need cut blocks at both ends of alternate courses.

Waste: order 5–10% extra blocks (8% staggered) for cuts, chipped corners, and dye-lot matching.

Costs: national-average material estimates — confirm local pricing and engineering requirements before building.