How many courses will my wall need?

Courses equal the wall height divided by the block height, rounded up. A 36 inch wall built from 6 inch tall blocks needs 6 courses. The tool computes this and uses it to count both the field blocks and the cap units.

What is the setback or batter?

Most segmental blocks step back a small amount each course, often around 1 inch, which leans the wall into the slope for stability. It barely changes the block count but is why tall walls need engineering. The tool reports the total lean.

When do I need geo-grid or deadman anchors?

NCMA and most manufacturers recommend soil reinforcement on walls taller than about 3 to 4 feet, typically a geo-grid layer every 2 courses. The tool estimates that count, but any wall over 4 feet usually needs an engineer and a permit.

How much drainage stone do I need?

A clean crushed-stone drainage zone roughly 12 inches deep behind the wall is standard. The tool multiplies wall face area by that depth to estimate the aggregate volume in cubic yards so you can order it with the blocks.

Is this an engineered design?

No. It estimates quantities for ordering only. Bearing capacity, global stability, surcharge loads, and reinforcement design for walls over about 4 feet require a licensed engineer and local permits. Use this as a planning tool.

Retaining Wall Block Count Calculator

A segmental retaining wall is a kit of parts: field blocks, caps, geo-grid, and a drainage zone. This calculator turns a height and length into a full quantity takeoff so you can price and order the job, and it flags when the wall is tall enough to need engineering.

How it works

Quantities flow from the course count and the wall face area:

courses        = ceil(wall height in / block height in)
blocks/course  = ceil(wall length in / block length in)
field blocks   = courses × blocks/course
cap units      = blocks/course
geogrid courses= floor(courses / 2)   (≈ every 2 courses when reinforced)
total setback  = (courses − 1) × per-course setback
drainage (yd³) = wall length ft × height ft × (12 in / 12) / 27

The drainage estimate assumes a 12 inch deep clean-stone zone behind the full face of the wall, which is the common detail for free-draining backfill.

Example and tips

A 24 ft long, 3 ft tall wall in 6 inch tall by 12 inch long blocks needs 6 courses of 24 blocks, so 144 field blocks plus 24 caps. That is right at the height where geo-grid reinforcement starts, about 3 grid courses. Order roughly 2.7 cubic yards of drainage stone for a 12 inch zone. Compact the base, build on a level leveling pad, and call an engineer before exceeding 4 feet of exposed height.