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Primary Consolidation Settlement Calculator

Estimate the long-term primary consolidation settlement of a compressible clay layer under a new load, per classic 1D consolidation theory.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Primary consolidation settlement

5.78 in

Check your inputs

This gives ultimate PRIMARY consolidation settlement only, assuming the clay is normally consolidated — overconsolidated clays need a modified formula with the preconsolidation pressure, and secondary (creep) settlement is not included here.

Equivalent in meters
0.48 ft

For the dimensions entered, expect a primary consolidation settlement of 147 mm. Note that added stress (δσ) sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. Moderate confidence — sound arithmetic, but allow for the variation any real site introduces. Set for United States against IRC 2024. The market selector changes both the units and the code cited.

Add the equipment this sizes

This result is a specification — 5.777 in — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Terzaghi 1D primary consolidation settlement: Sc = (Cc x H / (1 + e0)) x log10((σ'0 + Δσ) / σ'0), where Cc is the compression index, H is the clay layer thickness, e0 is the initial void ratio, σ'0 is the initial effective stress, and Δσ is the added stress

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Frequently asked questions

What is 'primary' consolidation settlement?
It's settlement from pore water being squeezed out of the clay's void spaces under load — the dominant, longest-duration settlement mechanism for saturated clay, distinct from immediate (elastic) settlement and secondary (creep) settlement.
How long does primary consolidation take?
It depends on the clay's coefficient of consolidation and the drainage path length — it can range from months to many decades for thick clay layers with limited drainage, which is why consolidation settlement is often a long-term concern rather than an immediate one.
What if my clay is overconsolidated?
This formula assumes normally consolidated clay. Overconsolidated clay (previously subjected to higher stress than currently present) settles much less until the added stress exceeds its preconsolidation pressure — a different, two-part formula applies in that case.