Retaining Wall Block Calculator
Estimate the blocks for a segmental retaining wall. Enter the wall length and height and your block size, then choose whether to add a cap course on top.
How to calculate retaining wall blocks
- Enter the wall length and finished height in feet.
- Set your block face length and height in inches, or keep the 12 by 8 default.
- Toggle a cap course, then read the blocks per course and the total.
Examples
20 ft long, 3 ft high, 12x8 in blocks, with cap
Length 20 ft, height 3 ft, block 12 x 8 in, cap on
20 per course, 5 courses, 100 wall + 20 cap = 120 blocks
Frequently asked questions
How many blocks do I need for a retaining wall?
Divide the wall length by the block length for one course, and the height by the block height for the number of courses. Multiply the two, then add a cap row if used.
How many courses high can a wall be?
Many segmental walls over about 3 to 4 feet need engineering, geogrid reinforcement and a permit. Check local rules before building tall, and step or terrace high slopes.
Do I need cap blocks?
Caps are optional but recommended. They give a clean, finished top edge and are usually glued down with concrete adhesive to lock the wall together and shed water.
What about the buried base course?
Bury the bottom course about one inch of wall height for every foot of height. Add height for that buried row so the calculator includes the hidden base blocks.
Does this include gravel backfill or base?
No. It counts wall and cap blocks only. Plan separately for a compacted gravel base, drainage stone behind the wall and a perforated drain pipe at the bottom.
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