Retaining Wall Calculator
Estimate retaining wall block courses, blocks per course, total blocks, cap units, base gravel and material cost from wall size, block size, waste and your prices.
Interactive calculator · Method RETAINING-WALL-1.0 · Last reviewed: 2026-11-04
Calculate your scenario
Exposed courses = exposed height ÷ block face height, rounded up; total courses add the buried courses.
Your inputs
Default worked example. Edit the inputs to calculate your scenario.
Default worked example
5 courses × 40 blocks = 200 blocks; × 1.05 waste factor, rounded up = 210 blocks. Built exposed height = 4 × 6 in = 24 in before the cap.
How to use the calculator
Measure the wall length along its face and the exposed height above finished grade. Enter the block and cap face sizes from the product sheet, how many courses will sit below grade, a waste allowance and your quoted prices. Enter the base trench width and gravel depth for a gravel estimate, or 0 to skip it.
What the result means
A 40 ft wall with 24 in exposed in 6 in blocks needs 4 exposed courses plus 1 buried, 40 blocks per course, so 200 blocks become 210 with 5% waste, plus 42 caps, for $903.00 at the example prices.
Formula and units
Exposed courses = exposed height ÷ block face height, rounded up; total courses add the buried courses. Blocks per course = wall length × 12 ÷ block face length, rounded up. Total blocks = courses × blocks per course × (1 + waste %), rounded up. Caps = wall length × 12 ÷ cap length × (1 + waste %), rounded up. Cost = blocks × block price + caps × cap price. Base gravel = length × trench width × gravel depth (inches converted to feet), ÷ 27 for cubic yards.
Worked examples
40 ft wall, 24 in exposed, 12 × 6 in blocks with caps: Wall length: 40 ft; Exposed wall height (above finished grade, excluding cap): 24 in; Buried courses below grade: 1 courses; Block face length: 12 in; Block face height: 6 in; Cap face length: 12 in; Waste and breakage allowance: 5 %; Price per block (example): 3.5 $ per block; Price per cap (example): 4 $ per cap; Base trench width (0 to skip gravel): 24 in; Base gravel depth (0 to skip gravel): 6 in; Cap row on top: yes.
Example result: Total blocks (with waste): 210 blocks; Courses: 5 (4 exposed + 1 buried); Blocks per course: 40 blocks; Cap units (with waste): 42 caps; Block and cap cost: $903.00; Base gravel volume: 40 ft³ (1.4815 yd³).
25 ft wall, 30 in exposed, 16 × 8 in blocks, no caps: Wall length: 25 ft; Exposed wall height (above finished grade, excluding cap): 30 in; Buried courses below grade: 1 courses; Block face length: 16 in; Block face height: 8 in; Cap face length: 12 in; Waste and breakage allowance: 10 %; Price per block (example): 6.25 $ per block; Price per cap (example): 4 $ per cap; Base trench width (0 to skip gravel): 18 in; Base gravel depth (0 to skip gravel): 6 in; Cap row on top: no.
Example result: Total blocks (with waste): 105 blocks; Courses: 5 (4 exposed + 1 buried); Blocks per course: 19 blocks; Cap units (with waste): 0 caps; Block and cap cost: $656.25; Base gravel volume: 18.75 ft³ (0.6944 yd³).
Limitations and common mistakes
Material quantities only. This does not decide whether a wall height, drainage, geogrid, footing, setback or block system is adequate; that comes from the block maker’s design tables, local rules and, where needed, an engineer. The count treats the wall as one straight run: corners, curves, steps, end returns and corner blocks are not counted separately. Prices and the waste allowance are your entries; defaults are examples. Gravel volume is the trench volume only; drainage aggregate behind the wall and compaction allowance are not included.
Using the full block depth or the nominal size instead of the face length and face height, or forgetting the buried course, which undercounts blocks.
Sources and assumptions
Method RETAINING-WALL-1.0; last formula review 2026-11-04. Sources and their supported claims. Calculation methodology.