Retaining Wall Calculator — Blocks, Gravel, Drainage & Cost
Estimate a segmental retaining wall from editable block geometry. Calculate courses, blocks, pallets, caps, base and drainage aggregate, pipe, fabric, excavation and cost.
7 total courses · 5 pallets · 5.50 yd³ aggregate.
Aggregate to order
- Base stone1.22 yd³ · 22.2%
- Drainage stone4.28 yd³ · 77.8%
- Block coresNot included
Core fill is not included. Enable it for hollow blocks that require aggregate.
Bar lengths show each material’s share of the total volume, including the aggregate allowance.
How the wall layers fit together
Course diagram, not to scale. Width, setback and drainage details are schematic; use the approved system detail. Large course counts are shown as grouped bands.
Requested: 3 ft · constructed exposed height: 3 ft
6 visible + 1 buried courses
Wall and block geometry
Enter the actual face dimensions from the selected block manufacturer. The course count rounds up so the built wall meets or exceeds the requested visible height.
Base, drainage and block fill
These are quantity assumptions, not a drainage or structural design. Match widths, depths, aggregate gradation, outlet and fabric placement to the approved wall system.
Optional current prices
Prices default to zero because local material and labor rates change. Enter delivered rates in one currency for a project-specific estimate.
Material takeoff
- Exposed + buried courses
- 6 + 1
- Blocks per course
- 30
- Blocks before waste
- 210
- Base aggregate
- 1.22 yd³
- Drainage aggregate
- 4.28 yd³
- Block core aggregate
- Not included
- Aggregate weight
- 7.70 short tons
- Filter fabric
- 195 ft²
- Base + drainage net volume
- 5.00 yd³
Net volume excludes buried block displacement, working space and reinforcement excavation. It is not total site excavation.
Cost audit
- Wall blocks
- —
- Caps
- —
- Aggregate
- —
- Pipe and fabric
- —
- Labor allowance
- —
- Other entered cost
- —
- Total estimate
- —
Quantity estimate only. Wall stability depends on soil, retained height, slope, surcharge, groundwater, embedment, setback and the selected system. Have geogrid, footing, drainage outlet and structural details reviewed where required. Check the manufacturer and local authority before construction.
How the retaining wall estimate works
Visible courses are the requested height divided by block face height and rounded up. Buried courses are then added. Blocks per course round up independently, and purchase waste is applied only after the full block count.
Base and drainage aggregate
Base volume is wall length × base width × compacted depth. Drainage volume is wall length × drainage-zone width × constructed wall height. The aggregate waste factor is added once to each component. Optional core fill uses installed blocks × the manufacturer’s per-block volume; spare purchase blocks are excluded. Net base and drainage volume is shown separately without purchase waste, not as total excavation.
Caps, pallets, pipe and fabric
Caps use their own face length and waste factor. Pallets round the purchase block count up to whole pallets. Pipe follows the wall with an editable allowance, while fabric wraps the constructed height, drainage width and entered overlap.
Retaining wall cost estimator
Enter current delivered material and labor rates; all defaults are zero. The calculator never substitutes a national average for your block system, aggregate source, access, equipment, disposal or contractor scope.
Soil for a separate planting area
If your project includes a planting bed, use the soil calculator to estimate its additional fill from the footprint, target depth and existing soil, then compare bags with a bulk order. Measure the planting area separately from the wall's drainage zone. Planting soil is not a substitute for the specified drainage aggregate or engineered backfill.
Design boundary and manuals
This tool does not calculate overturning, sliding, bearing, global stability, seismic loads or geogrid length. Many jurisdictions use height, slope and surcharge rules measured from different reference points. Follow the selected system's current manual and obtain a qualified design when the site, local code or manufacturer requires one. Compare the takeoff with a current primary guide such as the Allan Block residential installation manual or VERSA-LOK installation sequence; their details are product-specific and do not make the values here universal.
Frequently asked questions
How many retaining wall blocks do I need?
Divide wall length by block face length and round up for each course. Multiply by visible plus buried courses, then add the entered waste percentage and round up to whole blocks.
How much gravel goes behind a retaining wall?
The quantity here comes from your entered drainage-zone width and the constructed wall height. Use the aggregate type and minimum drainage-zone detail specified for the selected wall system.
Does this calculate geogrid or structural capacity?
No. Reinforcement and stability require site-specific soil, water, slope and surcharge information and are outside a material takeoff.
