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Retaining Wall Stability Calculator

Work out retaining wall stability instantly with clear inputs, formula shown and shareable results.

About Retaining Wall Stability Calculator

A gravity retaining wall is checked against two failure modes. Overturning compares the restoring moment of the wall's own weight about the toe with the moment of the active thrust, which acts at one third of the height for the soil triangle and mid-height for the surcharge rectangle. Sliding compares base friction, taken here at a coefficient of 0.5, with the horizontal thrust.

Formulas

Active thrust

Pa = 0.5 Ka gamma H² + Ka q H per metre of wall

Stability

FoS overturning = W x B/2 / (Pa moment); FoS sliding = 0.5 W / Pa

Worked example

With the default values below, Retaining Wall Stability Calculator returns Factor of safety against overturning of 3.463. Change any input above and every figure here is recalculated in your browser.

Inputs used

Wall heightminimum 0.1 m
3 m
Base widthminimum 0.1 m
2 m
Surcharge on retained soilminimum 0 kPa
10 kPa
Active earth pressure coefficientaccepts 0.1–1
0.33

Results

Factor of safety against overturning
3.463
Active thrust per metre
36.63 kN/m
Factor of safety against sliding
1.966
Average bearing pressure
72.0 kPa

Step by step

  1. 1Values used
  2. 2Active thrust
  3. 3Stability
  4. 4Factor of safety against overturning= 3.463
  5. 5Active thrust per metre= 36.63 kN/m
  6. 6Factor of safety against sliding= 1.966
  7. 7Average bearing pressure= 72.0 kPa

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Retaining wall design must be carried out by a qualified engineer including drainage, bearing capacity, global stability and reinforcement design.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Retaining wall design must be carried out by a qualified engineer including drainage, bearing capacity, global stability and reinforcement design.

Frequently Asked Questions

How is the Retaining Wall Stability figure worked out?

Pa = 0.5 Ka gamma H² + Ka q H per metre of wall. A gravity retaining wall is checked against two failure modes.

What factors of safety are needed?

Typically 2.0 against overturning and 1.5 against sliding, with bearing pressure inside the allowable value and the resultant kept within the middle third of the base.

What values do I need to enter?

This calculator takes 4 inputs: Wall height, Base width, Surcharge on retained soil, Active earth pressure coefficient. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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