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Retaining Wall Stability Calculator

§ Code basis: GB 50007-2011 (China) — The design equations differ, so the values are not interchangeable - recalculate with your own code.

Soil and surcharge produce moments at different heights; both factors of safety must pass.

Also known as retaining wall design · gravity wall check · wall stability

Quick answer

With the default inputs: Wall height H 3 m · Backfill friction angle φ 30° · Backfill unit weight γ 18 kN/m³ etc.Sliding factor of safety 1.75

Use your own dimensions ↓

Inputs

°
kN/m³
kPa
kN/m³

Result

Sliding factor of safety
1.75
Active coefficient Ka0.333
Soil pressure27.0kN/m
Surcharge pressure10.0kN/m
Total horizontal force37.0kN/m
Overturning moment42.0kNm/m
Restoring moment116.6kNm/m
Overturning FS (≥1.6 required)2.78
Sliding FS (≥1.3 required)1.75
Eccentricity e0.324m
Eccentricity limit 0.25B (GB 50007)0.450m
No-tension limit B/60.300m
Max base pressure150kPa
Min base pressure-6kPa
VerdictPass, but the base is in tension - widen it
How this is worked out

The two factors cover different failures: overturning is the wall rotating about its toe, sliding is the whole wall being pushed along its base. The two thresholds are not the same number: GB 50007-2011 clause 6.7.5 requires (Gn+Ean)mu/(Eat-Gt) >= 1.3 against sliding, (Gx0+Eaz·xf)/(Eax·zf) >= 1.6 against overturning, and a resultant eccentricity <= 0.25b. The easiest mistake here is the moment arms — soil pressure is triangular with its resultant at H/3, surcharge is rectangular at H/2. Combining them into one force at H/3 under-predicts the overturning moment. Once the eccentricity exceeds B/6 the base goes into tension and qmin comes out negative; in reality the heel lifts off and the pressure redistributes so qmax is higher than the formula. Clause 6.7.5 allows up to 0.25b, but a negative qmin still means widen the base or shift the stem back. qmax must also stay below the allowable bearing pressure fa, which this tool does not take as an input - check it against the site investigation. One thing this tool does not cover: water behind the wall. Without drainage the hydrostatic push can double the horizontal force, so always detail a filter layer and weep holes at 2-3 m centres, 50-100 mm diameter, staggered in two rows.

Next up: Pile Capacity Calculator · Bearing Capacity Calculator

Formula

Active coefficientKa = (1 − sinφ)/(1 + sinφ)
Soil pressurePs = 0.5·Ka·γ·H²
SurchargePq = Ka·q·H
Overturning momentMo = Ps·H/3 + Pq·H/2
Restoring momentMr = W·B/2
Sliding FSFSs = W·μ / Pa
Overturning FSFSo = Mr / Mo
Base pressureq = W/B·(1 ± 6e/B)
3 m wall, φ 30°, γ 18, 10 kPa surcharge, 1.8 m base, μ 0.5, wall at 24 kN/m³: Ka 0.333, 27.0 kN/m soil and 10.0 kN/m surcharge, 42.0 kNm/m overturning against 116.6 restoring, overturning FS 2.78 and sliding FS 1.75. Eccentricity is 0.324 m: all three clause 6.7.5 limits (1.3, 1.6, 0.25B = 0.45 m) are met, but it exceeds B/6 of 0.300 m, so the minimum base pressure is -6 kPa and the heel lifts. The verdict is pass, but widen the base.

Basis

The codes below are listed for comparison. This calculator returns GB 50007-2011 values only.

FAQ

How wide does a retaining wall need to be?
For a gravity wall the rule of thumb is a base width of 0.5 to 0.7 times the height, so a 3 m wall needs 1.5 to 2.1 m. That is only a starting point — check both factors of safety against sliding (1.3), against overturning (1.6) and the eccentricity (0.25B), all from GB 50007-2011 clause 6.7.5. The 3 m wall at 1.8 m above passes both factors at 1.75 and 2.78, yet the minimum base pressure is already negative, which means the centre of mass is too far forward; widen to about 2.1 m to clean it up.
Is drainage behind the wall really necessary?
Always. Once the backfill saturates, water pressure is isotropic and adds a push of half gamma-w h² on top of the active pressure — for a 3 m wall that is 44 kN/m, more than the 27 kN/m of soil pressure. Most retaining wall failures are drainage failures, not strength failures. Detail a 300-500 mm granular filter or geotextile-wrapped gravel drain, weep holes at 50-100 mm diameter and 2-3 m centres falling 5% outward, with the lowest row at least 300 mm above the ground in front.

What to calculate next

These jobs are done back to back on site — follow the steps to work through the whole sequence.

Retaining: pressure to supportStep 2 of 4

  1. 1Earth Pressure Calculator
  2. 2Retaining Wall Stability Calculator
  3. 3Soldier Pile Calculator
  4. 4Ground Anchor Calculator

Cite this page

Use this format in reports, method statements or coursework. The link is permanent.

Building Calculator. Retaining Wall Stability Calculator. 2026-10-25. https://jianzhujisuan.com/en/retaining-wall

Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.