Retaining Wall Calculator

Your details

The total horizontal run of the wall, measured along its face.
m
The finished height of the wall above the base course.
m
Length of one block as laid (a common SRW unit is about 45 cm / 18 in).
cm
Height of one block (a common SRW unit is about 20 cm / 8 in).
cm
Extra blocks for cuts at ends, corners and breakage. 5% to 10% is typical.
%
Cap stones finish the top course. The top field course is replaced by caps.
Length of one cap unit as laid. Often the same as the field block.
cm
Compacted gravel leveling pad depth (commonly 15 cm / 6 in).
cm
Trench width for the gravel base, typically about twice the block depth.
cm
Width of clean drainage stone behind the wall, at least 30 cm (12 in).
cm
Loose drainage gravel is roughly 1.4 to 1.7 t/m³; 1.5 t/m³ is a safe default.
t/m³
Currency
Wall blocks (with waste)
97
Cap stones (with waste)25
Courses (rows)5
Blocks per course23
Base leveling gravel0.72m³
Drainage backfill gravel3.3m³
Total gravel (cubic yards)5.26yd³
Total gravel weight6.03t

Order about 97 wall blocks for this wall.

  • Wall blocks = blocks per course × number of field courses, where each course is one row stacked up the wall height. The waste allowance is already included.
  • Add 25 cap stones to finish the top course; they replace the top field row.
  • Order about 0.72 m³ of base leveling gravel and 3.3 m³ of clean drainage backfill behind the wall (compaction and void allowances included).

Next stepFor walls over about 1.2 m (4 ft), or any wall holding back a slope or surcharge, have an engineer confirm the design, reinforcement and drainage.

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