Retaining Wall Material Estimator
Blocks and caps are only half the list. Enter your wall size and we add the base gravel and the drainage stone most first-timers forget — with a rough cost before you buy.
Your project
Walls over 4 ft usually need an engineer and a permit.
12″ of clean stone behind the wall is the standard.
Width of stone behind the wall face.
🪨 Retaining Wall Calculator
One top course to finish the wall.
6″ deep × 18″ wide compacted trench.
12″ of clean stone behind the wall.
🪨 Gravel Calculator
Bill of materials
| Material | Quantity | Est. cost | Note |
|---|---|---|---|
| Wall blocks | 132.00 blocks | $528 | |
| Cap blocks | 20.00 caps | $60 | Top course that finishes the wall. |
| Base trench gravel | 0.56 cubic yards | $25 | 6″ deep × 18″ wide compacted trench. |
| Drainage stone | 0.74 cubic yards | $33 | Clean ¾″ stone behind the wall. |
| Estimated material cost | $646 | Typical retail, plan only | |
Estimates use standard industry volume math and typical retail prices. Confirm quantities with your supplier — prices vary by region and season.
How this estimator works
The wall block and cap counts come from the retaining wall calculator using your length, height, and block face. The base gravel is the compacted trench under the first course, and the drainage stone is a separate volume behind the wall — both pulled from the gravel calculator using the drainage width and depth you set. The bill of materials combines them so nothing gets forgotten at the store.
Formula: Blocks = L×H ÷ block face × (1+waste); Base = L×1.5×0.5÷27; Drainage = L × width × depth÷12 ÷ 27
Good for
- Garden terraces and planting beds
- Slope retention up to 4 ft
- Raised patio edges
- First-time wall builders who want the full list
Tips
- Bury the first course — about 10% of wall height below grade for stability.
- Always backfill with clean stone and a perforated drain, never soil alone.
- Step the wall back as it rises (setback lip on most blocks).
- Anything over 4 ft retained usually needs an engineer and a permit.
Calculators used
References
Estimates use standard industry volume math. Cross-check your numbers against the pros:
Other project estimators
Retaining Wall Material Estimator FAQ
What materials do I need for a retaining wall?
Wall blocks, cap blocks for the top, compacted gravel for the base trench, and clean drainage stone behind the wall. Skipping the drainage stone is the most common DIY mistake — water pressure, not soil, topples walls.
How much does a retaining wall cost in materials?
Blocks run roughly $3–$6 each, caps a bit less, and gravel about $40–$55 per cubic yard delivered. The cost row uses typical retail as a planning estimate.
Why do I need drainage gravel behind the wall?
Freeze-thaw and rain load the back of the wall with water pressure. A 12-inch clean-stone column with a perforated drain at the base relieves that pressure and keeps the wall standing for decades.