Estimate retaining wall overturning factor of safety using simplified Rankine earth pressure theory. Enter wall height, retained soil height, soil unit weight, and base width to get overturning moment, resisting moment, and factor of safety vs. permanent (FS ≥ 1.5) and temporary (FS ≥ 1.25) wall requirements. For estimation only — all retaining wall designs require a licensed geotechnical or structural engineer.
Retaining wall stability against overturning is checked by comparing the resisting moment (from wall self-weight and soil above the footing heel) to the overturning moment (from lateral earth pressure). The factor of safety FS = Resisting Moment ÷ Overturning Moment must meet minimum thresholds: FS ≥ 1.5 for permanent walls and FS ≥ 1.25 for temporary structures per typical geotechnical practice.
Lateral earth pressure is estimated using Rankine active pressure theory, assuming a friction angle of 30° (Ka ≈ 0.333) — a conservative assumption for typical granular backfill. The active pressure resultant Pa = 0.5 × Ka × γ × H² acts at H/3 above the base, creating the overturning moment about the toe.
Permanent walls require FS ≥ 1.5 against overturning; temporary walls ≥ 1.25. FS = Resisting Moment ÷ Overturning Moment. Higher FS may be required by geotechnical reports or local codes.
Rankine theory calculates lateral soil pressure for cohesionless soil. Ka = (1 − sin φ) / (1 + sin φ). For φ = 30°, Ka ≈ 0.333. Active resultant Pa = 0.5 × Ka × γ × H², acting at H/3 above the base.
Rule of thumb: base width = 0.5–0.7 × wall height. For an 8 ft wall, 4–5.6 ft is typical. The base must resist overturning, sliding, and keep bearing pressure within allowable limits.
Complete design checks: overturning (FS ≥ 1.5), sliding (FS ≥ 1.5), bearing capacity (FS ≥ 3.0), and global stability (FS ≥ 1.5). This tool only checks overturning. A licensed engineer is required for actual design.
Simplified overturning factor of safety estimation using Rankine earth pressure theory. For estimation only.
Laser levels and GPS for retaining wall layout and grade control.
Shop Express Tools →Permanent walls require FS ≥ 1.5 against overturning; temporary walls ≥ 1.25. FS = Resisting Moment ÷ Overturning Moment. Higher FS may be required by geotechnical reports or local codes.
Rankine theory calculates lateral soil pressure for cohesionless soil. Ka = (1 − sin φ) / (1 + sin φ). For φ = 30°, Ka ≈ 0.333. Active resultant Pa = 0.5 × Ka × γ × H², acting at H/3 above the base.
Rule of thumb: base width = 0.5–0.7 × wall height. For an 8 ft wall, 4–5.6 ft is typical. The base must resist overturning, sliding, and keep bearing pressure within allowable limits.
Complete design checks: overturning (FS ≥ 1.5), sliding (FS ≥ 1.5), bearing capacity (FS ≥ 3.0), and global stability (FS ≥ 1.5). This tool only checks overturning. A licensed engineer is required for actual design.
Height of soil retained on the back of wall
Typical range: 95–130 pcf. Default 110 pcf.
Rule of thumb: 0.5–0.7 × wall height
| Failure Mode | Permanent FS | Temporary FS |
|---|---|---|
| Overturning | ≥ 1.5 | ≥ 1.25 |
| Sliding | ≥ 1.5 | ≥ 1.25 |
| Bearing (soil) | ≥ 3.0 | ≥ 2.0 |
| Global stability | ≥ 1.5 | ≥ 1.25 |
Typical values per ASCE 7 and geotechnical practice. Project-specific requirements supersede these defaults.