Retaining Wall Calculator — Blocks & Base
Enter your dimensions for an instant answer — the exact quantity to buy (waste included), a material cost, and an estimated installed cost. Change any figure to update the result live.
Your project
Standard size shown by default. Change any value — the answer recomputes instantly.
You need
126blocks
Exact need: 120 blocks · plus 5% waste allowance
Material cost
$315–$1,008
Installed (US avg)
$1,590–$2,733
Shopping list
| ITEM | QTY | PRICE RANGE |
|---|---|---|
| blocks | 126 | $315–$1,008 |
| Estimated material total | $315–$1,008 |
Companion materials
- Gravel base (6 in): ≈ 0.54 tons
Material spec & worked example
Waste allowance
5%
Typical price
$2.5–$8 wall blocks
20 ft long × 3 ft high: you need 120 blocks (buy 126 with waste), about $315–$1,008 in materials. See how we calculate this →
Popular sizes
Installed cost by state
See a regionally-adjusted installed estimate — materials, labor, total.
View cost by state →Frequently asked
How many blocks for a retaining wall?
Divide the wall face area (length × height) by the face area of one block. A standard block faces about 0.5 sq ft, so a 20×3 ft wall needs roughly 120 blocks.
How much base for a retaining wall?
Plan a 6-inch compacted gravel base one foot wider than the wall; the calculator estimates the tonnage.