A retaining wall calculator estimates how many segmental wall blocks and caps you need, including the buried first course, plus the gravel base, drainage stone, drain pipe, fabric, and cost. Enter one or more wall sections for a straight or stepped wall. Everything is calculated privately in your browser.
Enter the wall length and exposed height, then select Calculate wall. Or load an example.
Measure the length and the exposed height above finished grade in feet. Add a section for each height in a stepped wall.
Choose a block preset or enter the face length, height, depth, cap length, and pallet count from your supplier.
Keep the 6 in gravel base and 12 in drainage stone defaults or enter your own design values and waste allowance.
Enter optional unit prices, calculate, then review blocks, caps, pallets, gravel, stone, pipe, fabric, adhesive, cost, and height warnings.
Divide the wall length in inches by the block face length to get blocks per course, then multiply by the number of courses. Count the exposed courses plus at least one buried course, and add about 5 percent for cuts. A 20 ft wall of 16 in blocks needs 15 blocks per course.
Most block makers say to bury at least 6 in, or 1 in for every 8 in of total wall height, whichever is more. For 4 ft of exposed wall that is about 7 in, so two courses of 6 in block. Sloped ground in front of the wall needs more.
A typical base trench is 6 in of compacted crushed stone, as wide as the block depth plus 6 in in front and 6 in behind. For 10 in deep block that is 22 in wide. This calculator converts the volume to tons at 1.4 tons per cubic yard.
Yes. Place about 12 in of clean drainage stone behind the blocks for the full height, a 4 in perforated drain pipe at the base that drains to daylight, and landscape fabric between the stone and the soil so fines do not clog it.
Many segmental block systems need geogrid reinforcement above about 3 ft. Under the International Residential Code, walls retaining more than 4 ft of unbalanced soil need an engineered design, and slopes, driveways, or parked cars above the wall lower that limit. Check your local code.
Count mortared cinder blocks, mortar bags, and grout for masonry walls.
Estimate gravel tons and yards for bases, paths, and drainage.
Count pavers, base gravel, and bedding sand for a patio at the wall.
Estimate topsoil or backfill for the bed behind the wall.
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