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The soil particles' specific gravity.
2.65-2.70 is typical for most mineral soils (quartz sand, silt, common clay).
The soil's dry unit weight, from a lab or field density test.
The DRY unit weight — the weight of solids in a unit volume — which is what comes out of an oven-dry test, not the bulk weight of the sample as it arrived. If you have bulk unit weight and moisture content, the dry figure is the bulk divided by one plus the moisture content as a decimal. Using bulk weight here reports a void ratio lower than the truth, which is the optimistic direction.
Void ratio
0.5755 (e)
- Equivalent porosity
- 36.53 %
They open the calculator with your figures already in it
Soil Void Ratio Calculator: 0.5755 (e) — 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)
- Standard soil phase relationship: void ratio e = (Gs x γw / γd) − 1, where Gs is specific gravity of solids, γw is the unit weight of water, and γd is the soil's dry unit weight
Inputs used
- Specific Gravity of Solids (Gs)
- 2.65
- Dry Unit Weight (γd)
- 105.04 pcf
Intermediate steps
- Equivalent porosity
- 36.53 %
What this calculation does not cover
- The dry unit weight has to be genuinely dry. There is no moisture content input, so the calculation cannot strip pore water out of a bulk or wet density — feed it an uncorrected nuclear-gauge or sand-cone wet unit weight and the void ratio comes back too low.
- It separates voids from solids, not water from air. There is no degree of saturation anywhere in the model, so the result carries no water content, no saturated or buoyant unit weight, and nothing about effective stress, buoyancy or seepage below the water table.
- Specific gravity is defaulted, not measured. 2.65 is a quartz-sand figure; carbonate, mica-rich, iron-rich, volcanic and organic soils sit away from it, and because void ratio is a ratio with one subtracted, a few percent of error in either input turns into a larger percentage error in e.
- Void ratio is an index property, not a design check. This is not compaction acceptance — that is a Proctor or relative density comparison against a laboratory maximum — and it is not a settlement, bearing capacity or liquefaction assessment. It does not replace a site investigation or a geotechnical engineer's sign-off.
- One sample, one point in the ground. Nothing here allows for layering across a site, for the oversize gravel and cobbles a field density test leaves out of the sample, or for the void ratio changing as the soil is loaded, drained or remoulded.
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
- Standard soil phase relationship: void ratio e = (Gs x γw / γd) − 1, where Gs is specific gravity of solids, γw is the unit weight of water, and γd is the soil's dry unit weight
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