Retaining Wall Calculator
Work out how many retaining wall blocks, rows, and cap units you need based on your wall length, height, and block size.
Wall blocks
70blocks
Cap blocks
14blocks
Blocks per row
14blocks
Total rows
6rows
Assumes the top row is capped with a separate cap unit. Add 5-10% extra blocks for cuts, corners, and breakage.
How the retaining wall calculator works
Retaining wall blocks are calculated as a simple grid: how many blocks fit across the wall's length, times how many rows fit up the wall's height. The top row is broken out separately since it's almost always finished with a dedicated cap unit rather than a standard wall block.
Formula: blocks per row = wall length (in) ÷ block width. Total rows = wall height (in) ÷ block height. Wall blocks = blocks per row × (total rows − 1). Cap blocks = wall length (in) ÷ cap block length.
Frequently asked questions
Divide your wall length by the block width to get blocks per row, divide wall height by block height to get the number of rows, then multiply. This calculator does that automatically and separates out the top cap row.
Most segmental retaining wall systems use a dedicated cap unit for the top row, which is usually a different (often longer or flatter) piece than the wall blocks below it. This calculator assumes a capped top row by default.
5-10% is standard to cover cuts at corners and ends, plus breakage during handling. Add that on top of the raw block count shown above.
Yes — segmental retaining wall blocks range widely in width, height, and depth by manufacturer and style. Always check your specific product's spec sheet and adjust the block width and height fields above.