Retaining Wall Block Calculator — How Many Blocks Do I Need?
Enter your wall length and height to get the number of 16x8 retaining wall blocks plus caps. No sign-up, no data stored.
Blocks needed
How retaining wall block count is estimated
- Blocks per course = ceil(wall length x 12 / block length).
- Courses = ceil(wall height x 12 / block height).
- Base blocks = per-course x courses.
- Caps = per-course count (one cap per block above), if enabled.
- Waste = +5% default for the end cuts at corners and curves.
The course math assumes a straight run. At corners you turn a block sideways (which changes one face), and on curves you either shim the joints or buy blocks designed to angle. Add the buried first course separately - it keeps frost from lifting the wall.
Wall size → block count reference
16x8 blocks, +5% waste, caps included.
| Wall length | Height 1 ft | Height 2 ft | Height 3 ft |
|---|---|---|---|
| 10 ft | 8 blocks | 16 blocks | 24 blocks |
| 20 ft | 16 blocks | 48 blocks | 48+ (5 courses) |
| 30 ft | 24 blocks | 48 blocks | 72 blocks |
| 50 ft | 40 blocks | 80 blocks | 120 blocks |
Last updated: October 2026 · Counts are for straight runs with 16x8 blocks; corners add 1-2 blocks and curves add 5-10% over the straight count.
Retaining wall FAQ
Drainage stone for about a foot behind the blocks, a perforated drain pipe at the base, and compacted backfill. Without drainage, water pressure is what pushes most block walls over - blocks rarely fail on their own.
Manufacturers offer adhesive or a lip-and-groove lock. Glue is faster and helps on straight walls; dry-stacking with the pins is standard for DIY. Either way, backfill each course before adding the next so the wall can't slide.
Retaining wall blocks run roughly $2-5 each, so a 48-block wall is about $100-240 in blocks, plus gravel, pipe and caps. Delivery and pallet charges add up - order by the full pallet if you can.
Most 16-in blocks pivot slightly at the joints, giving gentle curves (radius of about 4-6 ft). Tight curves need manufactured radius blocks or cut faces. Count 5-10% extra for curve fitting.
For walls under 3-4 ft, usually no - the mass of the blocks and drainage handle the load. Taller or loaded walls need rebar pinned into a concrete footing; that's when you want a quick consult with a structural engineer.
Related calculators & guides
How Many Retaining Wall Blocks Do I Need?
Course math, drainage layers and cap selection for block walls.
Read the guide →