Retaining Wall Calculator

This calculator prices a retaining wall and counts its materials from three inputs: the wall's length and height in feet and the facing material (concrete block, natural stone, timber or poured concrete). It does not design the wall. Soil type, wall thickness, footing size, reinforcement and stability against sliding and overturning are not part of the calculation.

The face area is length × height. Blocks or stones are the face area divided by the face of one unit (0.89 sq ft for a concrete block, 1.5 for stone, 2 for a timber), rounded up; poured concrete has no unit count. Material is priced per square foot of face ($15 block, $25 stone, $12 timber, $30 poured concrete) and labor at $20 to $40 per square foot, which gives the low and high totals. Gravel is added for a base 1 foot wide and 6 inches deep along the wall and for a drainage zone 1 foot wide the full height of the wall, both at $45 per cubic yard. These are fixed planning rates, not local prices.

Drainage behind the wall matters because water trapped in the soil adds pressure the wall was not built for. Height is where the code steps in. The 2021 International Residential Code exempts a retaining wall up to 4 feet, measured from the bottom of the footing to the top of the wall, from a building permit unless it supports a surcharge, such as a slope, a driveway or a building above it (Section R105.2). It requires a wall that retains more than 48 inches of unbalanced fill, or one over 24 inches that also resists loads other than soil, to be designed by accepted engineering practice with a safety factor of 1.5 against sliding and overturning (Section R404.4). These are model-code rules; your city or county adopts its own version and may be stricter, so ask the building department before you build.