Calculate concrete retaining wall blocks, buried base courses, cap stones, drainage backfill gravel, leveling pad aggregate, and drain pipe.
Specify wall span, block profile, and embedment depth
Total continuous linear span
Visible height above finished grade
Standard manufacturer modular sizing
Embedment depth prevents toe sliding
Architectural coping units on top course
158 Base Wall Blocks + 16 (10% Cut Waste)
1 full top coping row
9.8 m² total face
~5.4 US Tons
6" deep x 22" wide pad
4" perforated pipe
Blocks, caps & gravel
Setting blocks directly on surface grass causes the toe of the wall to blow out under lateral soil thrust. Building codes require burying at least 1 full course or 1 inch per foot of wall height. Our calculator automatically factors embedment depth into your total block count.
More than 80% of retaining wall failures occur not because the blocks failed, but because water pooled behind the wall. Trapped water creates hydrostatic pressure that doubles the overturning force. Our tool calculates the exact 12-inch drainage gravel column and pipe requirements.
A solid foundation prevents differential settling. The leveling trench must be at least 6 inches deep and extend 6 inches in front and behind the block footprint. Our engine computes the exact crushed stone aggregate tonnage needed to compact this pad.
Splitting segmental concrete blocks with a chisel or masonry saw creates discarded bats and corner waste. Forgetting a 10% buffer halts installation mid-project, leaving your excavated slope exposed to dangerous rainfall erosion.
Measure the exposed length and desired visible height above ground. If ground slopes along the run, step the foundation in 6-inch increments.
Select standard commercial 16"x6" blocks, 18"x8" heavy segmental units, or custom dimensions including rear alignment lips or fiberglass pins.
Factor in 1 or 2 buried base courses for lateral toe stability, and choose whether architectural coping cap stones will seal the top layer.
Examine total blocks with 10% cutting waste, drainage gravel backfill cubic yards, base pad tons, perforated pipe, and material budget.
A segmental retaining wall (SRW) relies on unit weight, inter-block friction, and setback batter to resist the active lateral earth pressure ($P_a$) exerted by retained soil. As moisture accumulates behind an unvented wall, groundwater creates hydrostatic pressure that can exceed 62.4 pounds per square foot per foot of depth, easily pushing unanchored concrete blocks outward.
Always excavate a trench 6 inches deeper than the buried block and pack with dense-graded crushed road base (#21A) compacted to 95% Standard Proctor density.
Install a continuous 12-inch column of angular 3/4-inch washed stone directly against the block backs wrapped in non-woven geotextile to prevent silt clogging.
Place a 4-inch perforated PVC or corrugated pipe holes-downward along the base gravel chimney pitched at 1% slope to daylight or a dry well.
Calculates exact block counts based on standard commercial block face dimensions (height x width).
Automatically factors mandatory buried base courses (1 block buried per 3 feet of exposed wall height).
Computes required cubic yards of clean backfill gravel and linear feet of perforated drain pipe behind the wall.
Recommends geogrid tie-back layer counts and roll square footage for walls exceeding 4 feet in height.
To find the number of blocks, divide the total wall face area (Length x Total Height including buried courses) by the face area of a single block (Width x Height). For example, a 30-foot long by 3-foot high wall built with standard 16" x 6" blocks (0.667 sq ft face) requires approximately 135 blocks plus 10% cutting waste, totaling about 149 blocks.
Burying the first course (embedment) prevents the base of the wall from sliding forward under lateral earth pressure. Standard engineering guidelines require burying at least 1 full block course, or a minimum of 1 inch of embedment for every 1 foot of exposed wall height (minimum 6 inches buried depth).
A standard retaining wall requires a minimum 12-inch (1 foot) wide column of clean, angular 3/4-inch crushed gravel directly behind the entire height of the wall face. The volume is calculated as: Wall Length (ft) x Wall Height (ft) x 1 ft / 27 = Cubic Yards. This gravel chimney relieves hydrostatic pressure by channeling water to the perforated base drain pipe.
Most municipal building codes require a certified structural engineer and geogrid soil reinforcement layers for any gravity retaining wall exceeding 4 feet (48 inches) in total height (including buried blocks), or walls holding a surcharge load such as a driveway, patio, or steep upward slope.
Use dense-graded aggregate such as crushed gravel with stone dust (e.g., #21A or road base crushed rock) compacted in 2-inch to 3-inch lifts to form a level 6-inch deep pad that is at least 6 inches wider than the block footprint on both sides. Never set retaining blocks directly on soft soil or round pea gravel.
Crushed stone tonnage, cubic yards, and delivery loads.
Trench volume, perforated pipe, and geotextile fabric.
Standard brick counts, mortar bags, and sand volume.
Decorative stone tonnage, coverage, and garden beds.
