Retaining Wall Calculator
Enter your measurements
Extra to cover cuts, breakage, and mistakes.
Results
- Wall blocks189 blocks
- Cap blocks30
- Wall face area90 sq ft
- Gravel base0.56 cubic yards
Estimated cost
per retaining-wall block (material)
Material cost is per wall block (concrete retaining wall block only); budget separately for cap blocks, compacted gravel base, drainage stone behind the wall, and block adhesive for cap courses. Installed cost is per face square foot of finished wall and typically includes labor, base prep, block setting, backfill compaction, and drainage fabric, but not permits or engineer fees for taller walls.
Estimate only — prices vary by region, supplier, and season. Get a local quote before buying.
This retaining wall calculator figures out how many wall blocks, cap blocks, and cubic yards of compacted gravel base your project requires. Enter your wall's length and height along with the face dimensions of the block you've chosen, and it returns totals you can hand directly to a supplier. Using a retaining wall calculator before you order prevents the common mistake of buying for face area alone and forgetting caps, base material, and waste. Retaining wall blocks are sold individually at most home centers and landscape suppliers, with face widths typically running 6, 8, or 12 inches and face heights of 4 or 6 inches — the most common "standard" block covers a 12-by-6-inch face. Plan for at least 5 percent waste on straight runs; add 10 percent or more if you have curves, steps, or frequent cuts. The gravel base calculation assumes a 6-inch-deep, 12-inch-wide compacted bed, which is the minimum most manufacturers specify for gravity-block systems up to about four feet tall.
How it’s calculated
Blocks = Wall face area ÷ block face size, plus waste. Caps = wall length ÷ cap length. Add a compacted gravel base.
Worked example
For a 30-foot-long wall standing 3 feet tall, built with standard 12-by-6-inch face blocks and a 5 percent waste allowance, the calculator returns 189 wall blocks and 30 cap blocks covering 90 square feet of wall face. The project also calls for 0.56 cubic yards of compacted gravel base — less than a full yard, but still enough that most homeowners will need a bulk delivery or at minimum several bags of paver base to get the job done right.
Inputs
- Wall length
- 30 ft
- Wall height
- 3 ft
- Block face width
- 12 in
- Block face height
- 6 in
- Waste / overage
- 5 %
Result
- Wall blocks
- 189 blocks
- Cap blocks
- 30
- Wall face area
- 90 sq ft
- Gravel base
- 0.56 cubic yards
- Estimated material cost
- $756 – $2,268
Materials & pricing near you
Retaining wall blocks are sold by the piece at big-box stores and by the pallet (typically 60–80 blocks) through landscape suppliers, where pallet pricing can run 10–20 percent lower per block. Basic tumbled-concrete blocks start around $4–$6 each; mid-grade textured or beveled blocks from major manufacturers run $6–$10; premium natural-split or large-format blocks can push past $12. Delivery minimums vary widely — urban areas often have a one-pallet minimum plus a flat delivery fee, while rural suppliers may require two or more pallets. Prices tend to rise in spring when demand peaks and can dip slightly in late fall. Walls over 4 feet tall (sometimes 3 feet in stricter jurisdictions) typically require an engineer's stamp and a building permit; check your local municipality before breaking ground.
Frequently asked questions
How do I measure my wall if it steps up or has a curve?
For a stepped wall, calculate each level as a separate section — multiply its length by its height, then add the face areas together before dividing by block face size. For a curved wall, measure along the face of the curve using a flexible tape or a string pulled tight, not a straight-line distance. Add at least 10 percent waste for curves because blocks need to be cut or staggered to follow the arc.
Does this calculator account for batter (the backward lean)?
The calculator works from the visible face area, which stays the same whether the wall batters back or stands plumb. Batter affects how far the wall base extends into the slope, but it does not change how many blocks cover the front face. Most segmental gravity blocks have a built-in setback lip or pin system that sets each course back about 3/4 to 1-1/4 inches from the course below — check your block manufacturer's installation guide for the exact setback, since it determines the wall's final lean angle.
What size gravel base does the calculator assume?
The default assumes a compacted gravel base 6 inches deep and 12 inches wide — a common specification for gravity retaining wall systems up to about 4 feet tall. Taller walls or sites with poor drainage may require a wider, deeper base; consult the block manufacturer's specs or a landscape engineer for walls exceeding 4 feet.
Can I use this calculator for natural stone or timber retaining walls?
This calculator is designed around concrete retaining wall blocks with uniform face dimensions. Natural fieldstone and dry-stack stone vary too much in size to produce a reliable block count, though the gravel base volume is still a useful estimate. Timber walls (railroad ties or pressure-treated 6x6 lumber) are typically calculated by linear feet of timber, not block count — a separate calculation method is needed for those materials.