In-Situ Dry Density Calculator
Field bulk density = soil mass in the cutter ÷ cutter volume; dry density = bulk density ÷ (1 + moisture content); percent compaction = dry density ÷ the lab maximum dry density × 100. A 1,000 cm³ cutter holding 1,950 g at 12% moisture gives 1,741 kg/m³ — 96.7% of a 1,800 kg/m³ maximum. Moisture: Soil Moisture Content Calculator.
How it's calculated: Bulk density = (cutter + soil − empty cutter) ÷ cutter volume; dry density = bulk density ÷ (1 + moisture ÷ 100); compaction = dry density ÷ maximum dry density × 100.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Bulk density = (Cutter + soil mass − empty cutter mass) ÷ Cutter volume
Dry density = Bulk density ÷ (1 + moisture content as a fraction)
Percent compaction = Field dry density ÷ Laboratory maximum dry density × 100
Run the calculation to see each step with your own numbers.
A 1,000 cm³ cutter, empty 800 g, full 2,750 g, 12% moisture, 1,800 kg/m³ lab maximum dry density.
Soil mass = 2,750 − 800 = 1,950 g
Bulk density = 1,950 ÷ 1,000 × 1000 = 1,950 kg/m³
Dry density = 1,950 ÷ 1.12 = 1,741 kg/m³
Compaction = 1,741 ÷ 1,800 × 100 = 96.7%
- The cutter is driven into undisturbed, level compacted fill with a sharp cutting edge and trimmed flush at both ends — a disturbed or poorly-trimmed sample biases the volume reading.
- Moisture content comes from a separate representative sample taken alongside the cutter (ASTM D2216) — the cutter sample itself is used only for the mass/volume (density) reading.
- The laboratory maximum dry density must be from the SAME compaction test method (standard or modified Proctor) specified for the project — mixing standard and modified Proctor references gives a misleading percent-compaction figure.
- What compaction percentage is usually required?
- Most earthwork and pavement specifications require 90–95% of the laboratory maximum dry density for general fill, and 95–100% for subgrade and pavement layers — check your project's actual specification, since it varies by agency and application.
- Standard or modified Proctor — does it matter?
- Yes, significantly — modified Proctor uses more compactive energy and gives a higher maximum dry density than standard Proctor for the same soil. Make sure the maximum dry density you enter was determined by the same Proctor method your project specification calls for.
- Why is moisture content measured separately from the cutter sample?
- ASTM procedure has you take a small moisture sample from material immediately next to the cutter (or from the cutter's own soil after the density reading), so the cutter's mass/volume reading isn't disturbed by removing material for oven-drying.
- How do you calculate field dry density?
- Divide the field bulk density by one plus the moisture content as a fraction. A bulk density of 1,950 kg/m³ at 12% moisture gives 1,950 ÷ 1.12 = 1,741 kg/m³.
- How is percent compaction calculated?
- Divide the field dry density by the laboratory maximum dry density from the specified Proctor test, and multiply by 100. 1,741 kg/m³ against a 1,800 kg/m³ maximum is 96.7%.
Test method & formulas
ASTM D2937, 'Standard Test Method for Density of Soil in Place by the Drive-Cylinder Method' — the North American equivalent of the core-cutter method, using the same mass/volume and moisture-correction arithmetic.
About the In-Situ Dry Density Calculator
The In-Situ Dry Density Calculator turns a drive-cylinder (core cutter) field sample into bulk density, dry density, and percent compaction against the target laboratory maximum dry density (from a Proctor test) — the standard compaction-control check for fill, subgrade and pavement layers. It follows the ASTM D2937 drive-cylinder method's arithmetic, the North American equivalent of the core-cutter technique.
What you enter
- Cutter/cylinder volume, V
- Empty cutter mass
- Cutter + soil mass
- Moisture content (from a companion sample) — Use the Soil Moisture Content Calculator on a sample taken alongside the cutter. 0 is a valid (oven-dry) reading.
- Laboratory maximum dry density (Proctor)
What you get back
- Field bulk (wet) density — kg/m³
- Field dry density — kg/m³
- Percent compaction — % of the laboratory maximum dry density.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Soil Moisture Content Calculator — Water content of a soil sample as a percentage of its dry mass, from the container, wet-soil and dry-soil masses.
- California Bearing Ratio (CBR) Calculator — California Bearing Ratio of a subgrade or base sample at 2.5 mm and 5.0 mm penetration, against the ASTM standard loads.
- Unconfined Compressive Strength Calculator — Unconfined compressive strength and undrained shear strength of a cohesive-soil sample from the peak load and corrected area.
Related articles
- Understanding In-Situ Dry Density — In-situ dry density testing confirms that compacted fill in the field actually achieved the density it was designed and specified to reach.
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