How to use this calculator
- Enter Wall length in ft.
- Enter Wall height in ft.
- Press Calculate. The highlighted row is your order quantity; the note beneath it translates the number into real-world terms.
Formula & constants
Standard SRW blocks cover ~0.33 sq ft of face: face area × 3 = blocks. Caps run one per 1.33 ft of length. Behind the wall: 12 in of clean drainage gravel with a perforated pipe at the base. Every default in the fields above is editable — when your supplier’s spec sheet lists a different density, coverage rate or price, enter that number instead. The waste and compaction allowances follow common trade practice; see our methodology page for the derivation of each formula and the standards it references.
Where this fits in the project
Hardscape follows the same layer logic as paving: excavate, place compacted base and bedding sand, then set surface units. Bulk organics like mulch and topsoil are ordered by the cubic yard.
How this connects to your project
No quantity stands alone — each material in the chain depends on the ones around it. These are the planning steps that pair with the retaining wall calculator:
- Concrete Block Calculator — Retaining walls use concrete blocks or segmental units.
- Paver Calculator — Retaining walls often accompany paver patios.
- Gravel Calculator — Gravel backfill provides drainage behind retaining walls.
- Excavation Calculator — Excavate for retaining wall footing and backfill.
- Concrete Footing Calculator — Large retaining walls need concrete footings.
- Rebar Calculator — Engineered retaining walls may need rebar.
- French Drain Calculator — Retaining walls need drainage similar to French drains.
- Compaction Calculator — Backfill behind retaining walls must be compacted.
Frequently asked questions
When does a retaining wall need engineering?
Over 4 ft of total height, any surcharge (driveway/slope above), or terraced walls closer than twice their height.
Why do retaining walls fail?
Water — nearly always. Missing drainage gravel and pipe lets hydrostatic pressure build and push the wall over.
Last verified: — prices reflect current national averages. See our methodology.
Estimates are for planning. Material densities, coverage rates and prices vary by region and supplier — confirm final quantities before ordering, and check local code where structural or electrical work is involved.