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Soil Unit Weight from Specific Gravity Calculator

Compute a soil's dry and saturated unit weight from its specific gravity and void ratio.

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

Dry unit weight

16.25 kN/m³

High confidence
Saturated unit weight
19.93 kN/m³

For the dimensions entered, expect a dry unit weight of 16.2 kN/m³. Of the working steps, saturated unit weight dominates at 19.9 kN/m³. 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 — 16.248 kN/m³ — 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

  • Standard soil phase relationships: dry unit weight γd = Gs x γw / (1 + e); saturated unit weight γsat = (Gs + e) x γw / (1 + e), where Gs is specific gravity of solids, e is void ratio, and γw is the unit weight of water

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Frequently asked questions

Why compute both dry and saturated unit weight?
Dry unit weight is used for compaction control and above-water-table analysis; saturated unit weight is needed for effective stress calculations below the groundwater table, where buoyancy reduces the soil's effective weight.
What is the 'buoyant' (submerged) unit weight?
It's the saturated unit weight minus the unit weight of water (γ' = γsat − γw) — used for effective stress calculations below the water table, since the soil is effectively buoyed up by the surrounding water.
Why does void ratio reduce unit weight?
A higher void ratio means proportionally more air or water space and less dense mineral solid per unit volume — looser (higher void ratio) soil is lighter for the same particle specific gravity.