Geotechnical Calculators
12 free geotechnical calculators — standards-based, with formulas, worked examples, and no sign-up.
Everything on a site ultimately bears on soil, and soil is the one material you neither specify nor manufacture — you characterize what is there. That is why the workflow in this category starts with classification: the USCS/AASHTO tool takes gradation and Atterberg limits through the Casagrande plasticity chart and hands you the group symbol that every subsequent correlation keys off. From there the path forks by problem: bearing capacity (Terzaghi/Meyerhof for strip, square, and circular footings), consolidation settlement on the e-log p′ curve for clays, or seepage via Darcy's law and flow nets.
Lateral problems have their own chain. The lateral earth pressure calculator gives Rankine active and passive coefficients and thrust with surcharge; the retaining wall tool builds on that with full Rankine/Coulomb theory plus overturning, sliding, and bearing stability checks and reinforcement design; the cantilever sheet pile tool solves embedment depth and maximum moment for the unanchored case. Under earthquake loading, Mononobe-Okabe adds the seismic increment to the static thrust, and the liquefaction tool runs the NCEER 1997 CSR-vs-CRR procedure to a factor of safety and a plain triggering verdict.
Two tools are field-facing rather than design-facing. Soil compaction checks relative compaction and air voids against a Proctor reference (ASTM D698) — the numbers a density gauge report needs to pass. And the SRW retaining block calculator is intentionally limited to gravity segmental walls of four feet or less, the height below which most codes allow construction without an engineered design; above that it points you to the engineered retaining wall tool instead.
All Geotechnical Tools
Retaining Wall Calculator
Retaining wall design with Rankine/Coulomb earth pressure, overturning/sliding/bearing stability checks, and reinforcement design for gravity and cantilever walls.
Soil Classification
Automatic USCS and AASHTO classification with Casagrande plasticity chart and grain-size analysis.
Bearing Capacity Calculator
Ultimate, gross, and net allowable bearing capacity of shallow footings (Terzaghi/Meyerhof).
Consolidation Settlement Calculator
Primary consolidation settlement of clay for NC and OC soils using Terzaghi theory.
Soil Compaction Calculator
Field dry density, relative compaction, air voids, and saturation against a Proctor maximum per ASTM D698.
Seepage Flow Calculator
Darcy law and flow-net seepage: hydraulic gradient, velocity, and discharge through soil masses.
Lateral Earth Pressure Calculator
Rankine active and passive earth pressure and thrust on retaining walls with surcharge and water table.
Slope Stability Calculator
Infinite-slope factor of safety for cohesionless, c-phi, and seepage cases.
Cantilever Sheet Pile Wall
Simplified cantilever sheet pile embedment depth in cohesionless soil using Rankine active and passive coefficients and a net-pressure moment balance about the toe: theoretical depth d0, design depth D = 1.2-1.3 d0, and the maximum bending moment.
Soil Liquefaction Triggering
Simplified Seed-Idriss / NCEER liquefaction-triggering analysis: cyclic stress ratio CSR, cyclic resistance ratio CRR7.5 from corrected SPT (N1)60, magnitude scaling factor and the factor of safety against liquefaction with a verdict.
Mononobe-Okabe Seismic Earth Pressure
Pseudo-static seismic active earth pressure on a retaining wall by the Mononobe-Okabe method: seismic inertia angle, coefficient KAE, static KA, total seismic thrust PAE, the Seed-Whitman dynamic increment and the point of application.
Retaining Wall Block Calculator (SRW ≤ 4 ft)
Segmental retaining wall block takeoff for simple gravity walls up to 4 ft of exposed height per NCMA-style practice: courses and blocks per course from standard 12x4x9, large 18x6x12, or custom block sizes with the buried base course included (the greater of 6 in or 10% of the exposed height), optional cap units one per block width of length, compacted leveling-pad gravel 6 in deep by the block depth plus 12 in wide with a 1.15 loose-to-compacted factor, and the 12-in clean drainage-rock column over the exposed height — taller, surcharged, or sloped-backfill walls are referred to the engineered retaining-wall calculator.
Frequently Asked Questions
The block wall calculator and the retaining wall calculator overlap — which one is for me?
Height decides. A landscape wall of segmental blocks up to 4 ft with level backfill and no surcharge is a materials problem — the SRW block tool counts blocks, courses, and drainage rock. Anything taller, surcharged, or terraced is an engineered structure: the retaining wall calculator runs the actual stability checks (overturning, sliding, bearing) that a building department will ask for.
Do I need the classification tool if I already have a geotech report?
Usually not — the report gives group symbols directly. The classification tool earns its keep when you have raw lab data (sieve curves, LL/PI) without an interpretation, or when checking that a reported symbol is consistent with the test values it cites. Classification drives friction angle and compressibility assumptions everywhere downstream, so an error there propagates.
When does seismic earth pressure actually matter for a wall?
Mononobe-Okabe adds a dynamic increment proportional to the site acceleration, applied higher up the wall than the static resultant — so it hits overturning hardest. For low walls in low-seismicity areas the increment is small and routinely neglected; for walls supporting structures in seismic regions, codes require it. Run the M-O tool with your site's kh and compare against the static thrust to see whether it moves your design.