Retaining Wall Design Calculator

This calculator applies Rankine's classical earth-pressure theory to a retaining wall, starting from the soil's internal friction angle φ. The active pressure coefficient, Ka = (1 − sinφ)/(1 + sinφ), quantifies how much lateral push the retained soil exerts on the wall as it's allowed to yield slightly outward — a higher friction angle (denser, more angular soil) means a lower Ka and less thrust, which is why compacted granular fill is preferred backfill. The passive coefficient Kp is Ka's reciprocal-like inverse and represents the much larger resistance soil offers when a wall is pushed into it, useful for checking resistance at an embedded toe. The total active force comes from two triangular/rectangular pressure distributions: the soil's own weight creates a triangular pressure that grows linearly with depth, integrating to 0.5 × Ka × γ × H² acting at H/3 above the base, while a uniform surcharge load on the ground surface adds a rectangular distribution of Ka × q × H acting at the mid-height, H/2.

Multiplying each force by its lever arm and summing gives the overturning moment about the toe — the value engineers compare against the resisting moment from the wall's own weight to check a minimum safety factor, conventionally 2.0. The total active force also equals the sliding force used to check base friction resistance, with 1.5 the typical minimum factor of safety. This calculator reports only the driving-side forces and coefficients; it does not include the wall's self-weight, footing dimensions, or resulting factors of safety, so those must be checked separately using your specific wall geometry and materials.