Retaining Wall Calculator

Retaining walls resist lateral pressure from soil at different elevations. This calculator provides a deliberately simplified gravity-wall check for early comparison of wall proportions. It applies Rankine active earth pressure to dry, level, cohesionless backfill. The active pressure coefficient is calculated from the soil friction angle. Lateral pressure increases linearly with depth, so the resultant force equals one half of soil unit weight times the coefficient times wall height squared times wall length. That force acts approximately one third of the wall height above the base. Wall self-weight is estimated with a concrete unit weight of 24 kilonewtons per cubic meter. The model treats the wall as a solid rectangular section, so volume is height times thickness times length. For the overturning check, self-weight acts at the center of the wall thickness. Resisting moment is therefore wall weight times half the thickness, while overturning moment is active earth force times one third of the height. Dividing resisting moment by overturning moment gives the displayed factor of safety. A value of 1.5 is shown as a familiar preliminary comparison, not an approval criterion. Real retaining-wall design must also check sliding, bearing pressure, eccentricity, settlement, global stability, structural capacity, drainage, seismic loads, surcharges, frost, scour, and construction stages. A footing toe and heel can substantially change stabilizing weight and moment arms, but those elements are not represented by the simple rectangular model. Water pressure can dominate soil pressure when drainage fails and must never be ignored in final design. Soil friction angle and unit weight should come from site-specific geotechnical information. Cohesive soil, sloping backfill, compaction loads, nearby foundations, vehicles, fences, and stored materials require a more complete pressure model. Passive resistance is often limited or omitted because excavation, erosion, or utility work can remove soil in front of a wall. Appropriate load factors and resistance factors also depend on the governing design method and jurisdiction. Use this result to understand how height, thickness, and soil properties influence one basic overturning mechanism. Do not use it as construction documentation. Retaining wall failure can cause serious injury and property damage, so a qualified geotechnical and structural professional should evaluate site conditions, drainage, foundations, reinforcement, and code compliance before work begins.