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How it works
Yardaris rounds wall height up to complete block courses and wall length up to complete blocks per course, then applies the block waste allowance. It separately calculates compacted base gravel and drainage backfill volume in cubic yards. Cap blocks are estimated as one top row using the entered block face length.
Retaining wall calculator with cap blocks
This retaining wall calculator estimates both the wall blocks to order and the cap blocks needed for the top row. Wall blocks are based on the number of complete courses and blocks per course, with the entered waste or breakage allowance applied to the wall-block quantity. Cap blocks are calculated separately as one complete top row using the entered block face length.
Example: For a 20 ft long wall using 12-inch-long blocks, one complete top row requires 20 cap blocks. The wall height determines how many block courses are needed below the cap row, while the waste allowance is applied to the wall-block order quantity.
How many retaining wall blocks do I need?
Measure the wall length and exposed height in feet. Enter the block face length and height in inches. The calculator rounds up to complete blocks per course and complete courses, then adds the selected waste or breakage percentage. For stepped, curved, or irregular walls, estimate each section separately and combine the results.
Example: A wall 20 feet long and 2 feet high with blocks measuring 12 inches long by 4 inches high needs 20 blocks per course and 6 courses. That is 120 wall blocks before waste, or 132 wall blocks with a 10% waste allowance. The top row estimate is 20 cap blocks when cap length matches the entered block length.
Estimate retaining wall base and drainage gravel
Base gravel volume is wall length × base trench width × compacted base depth, with all dimensions converted to feet, divided by 27 to give cubic yards. Drainage gravel volume uses wall length × wall height × drainage backfill thickness, divided by 27. These are simplified rectangular estimates and do not include additional excavation, footing extensions, embedded courses or irregular shapes.
Planning reminder: This calculator estimates quantities only. Confirm foundation dimensions, drainage details, reinforcement, engineering and permit requirements for your chosen wall system and local conditions.