Landscape Retaining Wall Calculator Formula

Understand the math behind the landscape retaining wall calculator. Each variable explained with a worked example.

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Formulas Used

Blocks Needed

total_blocks = blocks_per_row * num_rows

Number of Rows

rows = num_rows

Wall Face Area

wall_face_sqft = wall_length * wall_height

Variables

VariableDescriptionDefault
wall_lengthWall Length(ft)30
wall_heightWall Height(ft)3
block_lengthBlock Length(in)12
block_heightBlock Height(in)4
blocks_per_rowDerived value= block_length > 0 ? ceil(wall_length * 12 / block_length) : 0calculated
num_rowsDerived value= block_height > 0 ? ceil(wall_height * 12 / block_height) : 0calculated

How It Works

Retaining Wall Block Count

Blocks per Row = Wall Length / Block Length

Rows = Wall Height / Block Height

Total Blocks = Blocks per Row x Rows

Add 5 to 10 percent for cuts and waste. Walls taller than 4 feet typically require engineering and may need geogrid reinforcement.

Worked Example

30 ft wall, 3 ft tall, using 12 x 4 inch blocks.

wall_length = 30wall_height = 3block_length = 12block_height = 4
  1. 01Blocks per row = ceil(360 / 12) = 30
  2. 02Rows = ceil(36 / 4) = 9
  3. 03Total = 30 x 9 = 270 blocks
  4. 04Add 10% waste = 297 blocks, order 300.

Ready to run the numbers?

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