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✓ NCMA National Concrete Masonry Association Standard

Retaining Wall Block & Base Calculator

Estimate interlocking segmental retaining wall blocks, capstones, leveling pad gravel, and drainage rock.

Wall Dimensions & Block Sizing

Height above ground
Retaining Wall Material Estimate
Wall Blocks Needed 174 Blocks 7 Courses Total
Cap Stones 25 Caps Top Finish Layer
Leveling Pad Base Gravel (6" deep): 0.83 cu yds (1.17 tons)
Drainage Backfill Gravel (12" chimney): 3.33 cu yds (4.67 tons)

Frequently Asked Questions

How deep should the base trench be for a retaining wall?

The base trench should be excavated at least 12 inches deep and 18 to 24 inches wide. Fill with 6 inches of compacted angular crushed stone (#57 or crusher run), and bury the first course of blocks completely underground for lateral stability.

How high can a DIY retaining wall be built without an engineer?

Most local building codes allow gravity block retaining walls up to 4 feet in total height (including the buried base course) without requiring a stamped engineered plan or geogrid soil reinforcement.

Why do retaining walls need gravel backfill behind them?

Water trapped behind a wall is the #1 cause of retaining wall failure due to hydrostatic pressure. A 12-inch wide vertical chimney of clean drain gravel (along with a perforated drain pipe at the base) allows water to drain freely away.