Courses
3 ft ÷ 6 in (0.5 ft) = 6 visible courses. Add 1 buried course → 7 total courses.
Retaining Wall Block Calculator
Estimate how many segmental retaining wall blocks to buy from the wall run and the product you will lay, plus cap blocks, compacted base aggregate, and drainage stone.
For a straight CMU block wall, use the standard concrete block calculator instead. For installed cost with labor, use the retaining wall cost calculator .
Unit:
Start the material takeoff
Measure from finished ground to the top of the highest regular wall unit. Do not include the cap or buried courses.
Wall block product
Live material estimate
Wall blocks to buy
178
161 before waste with 10% waste
Cap blocks to buy
33
Compacted base aggregate
1.11 cu yd
Free-draining drainage stone
3.89 cu yd
More wall and price settings
Planning assumption only. Confirm the required number with the product guide, plans, and site conditions.
Aggregate and drainage stone
These are geometric volumes only. They do not account for supplier density, delivery minimums, compaction, or site allowance.
Waste allowance10%
Use 5 to 10% for simple straight walls; increase for curves, cuts, or damaged blocks.
Material cost
Enable to enter local wall-block, cap-block, base-aggregate, and drainage-stone prices.
Is the number above the blocks I should buy?
Yes. Wall blocks to buy is the purchase count after waste, and it already includes the buried courses you entered. Cap blocks and the two gravel quantities are separate lines.
Caps stay extra
Cap blocks run along the top. They do not replace a regular wall-unit course, so do not subtract a course when a cap is included.
Visible height is only the exposed wall units
Measure from finished ground to the top of the highest regular wall unit. Do not put the cap or the buried courses into that height.
The two gravels are two orders
Compacted base aggregate sits under the wall. Drainage stone sits behind it. Keep those volumes as separate purchases.
How many retaining wall blocks does the sample buy?
The calculator starts on a 30 ft run and 3 ft visible height, using a 6 × 16 in wall block, one buried course, caps, and 10% waste. Use Reset to put this sample back.
Wall blocks to buy
30 ft ÷ 16 in rounds up to 23 blocks per course. 7 × 23 = 161 before waste. 10% waste → 178 to buy.
Cap blocks to buy
30 ft ÷ 12 in cap face = 30. 10% waste → 33 to buy. These are not included in the 178 wall blocks.
Separate gravel volumes
Base: 30 ft × 2 ft × 0.5 ft = 1.11 cu yd. Drainage stone: 30 ft × 3.5 ft total wall-unit height × 1 ft = 3.89 cu yd.
Where do you measure the wall and gravel zones?
Use the dimensions from the product guide and your project. The diagram shows where each calculator input sits. It is not a construction detail.
How does this calculator count retaining wall blocks?
It rounds visible wall-unit height up to whole courses, adds the buried courses you entered, then uses the wall run and the selected product face to count wall blocks and caps.
Compacted base aggregate and free-draining drainage stone are estimated as separate rectangular volumes. In imperial mode, the calculator converts cubic feet to cubic yards. In metric mode, it reports cubic meters.
Courses
ceil(visible height ÷ block height) + buried courses
It rounds up so a partial visible wall height still includes the next course of block. Buried courses are added separately.
Wall blocks
ceil(total courses × ceil(wall run ÷ block face length) × (1 + waste ÷ 100))
It uses the selected retaining wall block face length, then applies the waste allowance.
Cap blocks
ceil(ceil(wall run ÷ cap length) × (1 + waste ÷ 100))
It counts cap blocks separately because they do not replace a regular wall-unit course.
Separate aggregate purchases
base: run × width × depth; drainage: run × total height × zone depth
Base aggregate uses wall run, base width, and compacted base depth. Drainage stone uses wall run, total wall-unit height including buried courses, and drainage-zone depth.
Why the aggregate quantities stay separate
Compacted base aggregate
The base quantity is the rectangular volume below the wall. This calculator uses your wall run, base width, and base depth.
Free-draining drainage stone
The drainage quantity is the rectangular zone behind the block wall. This calculator uses wall run, total wall-unit height including buried courses, and drainage-zone depth.
Sources
Sources reviewed July 2026
Where this estimate stops
- Use this for a segmental retaining wall material estimate. It does not cover poured concrete or ordinary CMU walls.
- The optional prices cover materials only. For installed cost with labor, use the retaining wall cost calculator. They do not produce a contractor quote.
- The calculator does not design base dimensions, drainage design, geogrid, soil conditions, loads, or wall stability.
- For a curved wall, enter measured arc length. For a stepped wall, calculate each section separately. For multi-size patterns, use the manufacturer's pattern coverage.
Frequently asked questions
How should I enter a curved retaining wall?
Enter the measured arc length as the wall run. The calculator does not derive a radius or design wedge blocks, joints, setback, or layout. Check the product manufacturer for curve limits and installation rules before ordering.
Can I combine the aggregate quantities when ordering?
Keep compacted base aggregate and free-draining drainage stone as separate purchases. The calculator shows separate geometric volumes because each uses different inputs and may have different supplier prices. Confirm packaging, delivery minimums, compaction, and site allowance with the supplier.
Does visible height include the buried course or cap?
No. Enter the height from finished ground to the top of the highest regular wall unit. Add buried wall-unit courses separately. Cap blocks run along the top and do not replace a wall-unit course.
When should I get a professional review?
Get qualified local advice for walls affected by height, loads, slopes, terraces, soil, drainage, local code, or any condition that needs structural or site design. This calculator is for a material estimate only.
For installed cost with labor, use the retaining wall cost calculator .