Geotechnical Engineering
Percent Compaction Calculator
Calculate field dry density, percent compaction, density acceptance, and moisture-band status from field and Proctor test data.
Parameter sketch
Field density acceptance
Labels update with the current input values so the formula symbols stay tied to the geometry.
Result
Meets entered criteria: 95.5% compaction
Field dry density
112.73 pcf
Minimum required dry density
112.1 pcf
Percent compaction
95.5%
Density criterion
Pass
Moisture band
9% to 13%
Moisture criterion
Within band
Step-by-step calculation
- Convert moisture content to decimal: 10% / 100 = 0.1.
- Field dry density = 124 / (1 + 0.1) = 112.73 pcf.
- Percent compaction = 112.73 / 118 x 100 = 95.5%.
- Minimum required dry density = 118 x 0.95 = 112.1 pcf.
- Compare field moisture 10% with the entered band of 9% to 13%.
What this means
The field result meets both the entered relative-compaction requirement and moisture band.
Important limitations
- Acceptance must follow the project specification, test method, correction procedures, and authorized engineering judgment.
Assumptions
- Field wet density and laboratory maximum dry density use the same units
- The laboratory Proctor curve represents the material tested in the field
- Rock corrections and project-specific acceptance rules are handled separately
Formula Used
gamma_d = gamma_wet / (1 + w); RC = gamma_d,field / gamma_d,max x 100
Step-by-Step Example
A field wet density of 124.0 pcf at 10.0% moisture gives 112.73 pcf dry density. Compared with a 118.0 pcf Proctor MDD, relative compaction is 95.5%.
Engineering Notes
- Use the laboratory curve that represents the field material and required Standard or Modified Proctor effort.
- Density and moisture may be separate acceptance criteria; a density pass does not override a moisture failure.
- The calculation does not include oversize-particle corrections, test-location judgment, or method-specific bias.
FAQ
What is percent compaction?
Percent compaction, or relative compaction, is field dry density divided by the applicable laboratory maximum dry density, multiplied by 100.
Can density pass while moisture fails?
Yes. Some specifications require both a minimum relative compaction and a moisture range. The governing project requirements control acceptance.
Does the calculator apply rock correction?
No. Oversize-particle corrections and test-method limitations must be handled under the governing standard and project specification.