WALL BLOCK COUNT

Enter the wall length and finished height in feet. Pick the block size sold at your local home center — small landscape blocks (12 × 4 × 8 in, ~25 lb each) build short ornamental walls; standard blocks (16 × 6 × 10 in, ~60 lb) are the common residential choice; large blocks (18 × 6 × 12 in, ~85 lb) build taller walls but each one needs a wheelbarrow.

Choose whether to include cap blocks (caps finish the top course flat and are sold separately). The calculator returns total block count, blocks per course, course count, cap count, and base gravel needed for the leveling pad. Walls under 4 feet of exposed face are gravity walls a homeowner can DIY; over 4 feet typically requires geogrid soil reinforcement and engineered design.

For a 20 ft long, 2 ft high wall using standard 16×6×10 blocks with caps:

Blocks per course: ⌈(20 × 12) ÷ 16⌉ = 15 blocks. Courses: ⌈(2 × 12) ÷ 6⌉ = 4 courses. Total blocks: 15 × 4 = 60. Caps: 15.

Base gravel: 21 ft long × 1 ft wide × 6 in deep = 10.5 ft³ = 0.39 yd³. Round up to 0.5 yd³ at the supply yard.

At $4–$8 per standard block, $4–$6 per cap, and $40 per yard of gravel: materials run $310–$590. Pro install adds $25–$50/ft of wall in labor (~$500–$1,000), making installed cost $800–$1,600 for this wall. DIY is doable but heavy work — plan for 2 people and a full weekend.

For a 4 ft tall wall: jumps to 8 courses, 120 blocks, and triggers the engineered-design recommendation. Below 4 ft is the DIY sweet spot.

Skipping the leveling pad. A retaining wall built directly on dirt sinks unevenly and pushes outward within a year. 6 inches of compacted ¾-inch crushed stone, leveled with a long board and torpedo level, is non-negotiable.

Building over 4 feet without engineering. Walls over 4 feet of exposed face hold significantly more soil pressure than gravity walls can resist. Geogrid (soil reinforcement strips that extend back into the slope) is required, plus an engineered design and usually a permit.

Forgetting drainage. Water building up behind the wall pushes hard. Install a 4-inch perforated drain pipe in 1–2 feet of crushed stone behind the first course, run to daylight or a French drain. Without this, walls bulge and topple.

Setting the first course at grade. The bottom course should be buried 1 inch per foot of wall height (so a 3-ft wall has the first course buried 3 inches). This anchors the wall against forward sliding.

Small landscape blocks (12×4×8): ~25 lb, builds walls up to 2–3 ft.

Standard blocks (16×6×10): ~60 lb, builds gravity walls up to 4 ft.

Large blocks (18×6×12): ~85 lb, builds taller walls (still requires engineering above 4 ft).

Base: 6 inches of compacted ¾-inch crushed stone, 12 inches wider than the block face.

Drainage: 4-inch perforated drain pipe + crushed stone behind the wall, run to daylight.

Bury 1 inch per foot of wall height for stability.