Retaining wall block calculator

Block count chart for 12 common wall sizes

With generic 16-inch-long × 6-inch-high face units, one buried course and 10% cutting allowance, the counts below round every course and the final order upward. Heights are exposed blockwork, with caps excluded. These are quantity examples, not approved wall designs.

Use your actual installed module, embedment and layout for an order. Special units and full-pallet purchasing are separate. Changing a height across a course boundary can add a whole row.

Choose installed block dimensions

Select a reference preset or enter the actual length, height and depth. The selector changes dimensions only; packaging, caps, core fill, base and drainage assumptions remain yours to verify. The full manufacturer table and catalog notes are kept in the block-size guide.

How many retaining wall blocks do I need?

A face-area shortcut divides total wall area by the area of one block. That can be a useful early check, but it does not round the ends of each course or a partial top course. Course counting is a better starting point for an order list. This tool rounds the run of each course, rounds the exposed courses, adds your buried courses, and finally applies waste.

If a block is tapered, split-faced, or part of a modular pattern, use its effective installed coverage. Do not use the widest decorative face as a module length unless the manufacturer specifies that measurement. Enter special corners, half units and end units separately in your supplier schedule.

Order blocks = ceil(ceil(length ÷ module length) × (ceil(height ÷ module height) + buried courses) × (1 + waste/100))

Retaining wall block waste and pallet counts

Waste is an allowance for cuts, handling damage and uncertain takeoff details. Five, ten and fifteen percent are convenient planning choices, not measured product loss rates. The actual allowance depends on the layout, whether cuts can be reused, and your supplier’s returns policy.

The pallet count rounds the order quantity up to a whole pallet using the number of units you enter. The starting 75 units is illustrative, not a standard package across brands. Buying whole pallets can give you more units than the displayed unit takeoff. Check the product listing before approving delivery.

Example: how many blocks for a 20-foot wall?

With a 20-foot run, 3 feet of exposed height, 16-inch-long × 6-inch-high units, one buried course and 10% allowance, order 116 blocks (105 net). The run takes 15 units per course, and six visible courses plus one buried course produce the 105-unit net count.

At 37 inches of exposed height, order 132 blocks (120 net). The partial height requires seven full exposed courses; adding the buried course gives eight courses × 15 units. This is why a one-inch height change can add a complete course, not because the calculator applies an area-only shortcut.

How many retaining wall blocks per square foot?

A generic 16 × 6 inch installed face needs about 1.5 blocks per square foot of wall face. An 18 × 8 inch installed face covers 1 ft², giving 1 block per square foot. Use the installed face length and height; block depth does not determine face coverage.

This is a rough area check. It excludes buried courses, cutting allowance, caps and rounding at the ends or top of the wall. Use the course-based calculator above for an order. For tapered faces or mixed-size patterns, use the manufacturer’s stated installed coverage.

Face area (ft²) = installed face length (in) × course height (in) ÷ 144
Blocks per ft² = 144 ÷ (installed face length (in) × course height (in))