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The depth of soil in front of the wall or footing providing passive resistance.
This is typically much shallower than the retained (active side) height, since it's just the soil in front of the footing toe.
The soil's angle of internal friction.
Passive pressure is the case where optimism costs most, because it is resistance you are RELYING on rather than load you are resisting — overstate the angle and you overstate the help the ground gives. Many designers reduce it deliberately here for that reason. The other half is movement: passive resistance needs the wall to push into the soil to develop, and far more movement than active pressure needs, so a wall that must not visibly move cannot count on the full value.
The soil's unit weight in front of the wall.
In FRONT of the wall, which is frequently not the same material as the retained fill behind it and is often the weaker of the two, because it has been dug out and put back. Where the excavation in front is temporary or could be dug again by someone else later, the honest passive resistance may be none at all. Below the water table use the submerged weight and carry the water pressure as its own term.
Passive pressure resultant
688 lbf/ft
Passive resistance is often unreliable in practice — it requires enough wall movement to mobilize, and can be lost entirely if the soil in front of the wall is later excavated or erodes. Many designers deliberately ignore or heavily discount passive resistance for this reason.
- Rankine passive coefficient (Kp)
- 3
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Rankine Passive Earth Pressure Calculator: 688 lbf/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Rankine passive earth pressure coefficient: Kp = tan²(45° + φ/2); passive pressure resultant: Pp = 0.5 x Kp x γ x H²
Inputs used
- Embedment Depth (Passive Soil Height)
- 2 ft
- Soil Friction Angle (φ, degrees)
- 30
- Soil Unit Weight γ
- 114.59 pcf
Intermediate steps
- Rankine passive coefficient (Kp)
- 3
Confidence note: Passive resistance is often unreliable in practice — it requires enough wall movement to mobilize, and can be lost entirely if the soil in front of the wall is later excavated or erodes. Many designers deliberately ignore or heavily discount passive resistance for this reason.
What this calculation does not cover
- There is no water in this model. Below the water table the soil in front of the wall contributes only its buoyant weight, so the resistance from the soil skeleton is far less than the full unit weight entered here suggests, and the water pressure acting on the same face is a separate term this does not compute. Perched water, seepage and a table that rises after rain are not checked at all.
- Rankine here is the cohesionless case against a smooth vertical wall face with level ground in front of it. There is no cohesion term, no wall friction or adhesion, no allowance for ground that falls away from the toe (which reduces passive resistance), and no layering — a single friction angle and unit weight cannot describe soft clay, mixed fill, or a granular layer over something weaker.
- This is the full theoretical passive resistance with no factor of safety and no mobilisation reduction applied. Passive pressure needs far more wall movement to develop than active pressure does, so the resistance actually available at a deflection the structure can tolerate is a fraction of this figure. Deciding how much of it to count is a design judgement the calculator does not make.
- The whole embedment depth entered is treated as effective passive soil. Nothing is subtracted for a frost-affected or disturbed upper zone, topsoil or paving buildup, or for soil that a future utility trench, re-grade or landscaping in front of the wall would remove.
- This is one force per metre run of wall, not a stability check and not a design. It does not check sliding, overturning, bearing pressure, base heave or global slope stability, does not size or reinforce the wall or footing, and includes no load factors and no seismic case. Passive resistance is one term in a check that a qualified engineer has to complete against site-specific geotechnical data.
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This result is a specification — 688 lbf/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Rankine passive earth pressure coefficient: Kp = tan²(45° + φ/2); passive pressure resultant: Pp = 0.5 x Kp x γ x H²
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