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Soil Compaction Calculator

Work out soil compaction instantly with clear inputs, formula shown and shareable results.

About Soil Compaction Calculator

Relative compaction is field dry density divided by the maximum dry density obtained in a Proctor test, expressed as a percentage. Specifications normally require 95 percent of standard Proctor for general fill and 98 percent beneath pavements, because density controls settlement and shear strength directly.

Formulas

Relative compaction

RC = field dry density / maximum dry density x 100

Required density

Required = maximum dry density x specified percentage

Worked example

With the default values below, Soil Compaction Calculator returns Relative compaction achieved of 92.97%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Field dry densityminimum 0.1 g/cm³
1.72 g/cm³
Maximum dry density from Proctorminimum 0.1 g/cm³
1.85 g/cm³
Specified compactionaccepts 50–105 %
95 %

Results

Relative compaction achieved
92.97% %
Compliance
Below specification — further compaction required
Density needed to comply
1.758 g/cm³
Density shortfall
0.038 g/cm³

Step by step

  1. 1Values used
  2. 2Relative compaction
  3. 3Required density
  4. 4Relative compaction achieved= 92.97 %
  5. 5Compliance= Below specification — further compaction required
  6. 6Density needed to comply= 1.758 g/cm³
  7. 7Density shortfall= 0.038 g/cm³

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Compaction acceptance must follow the project specification and be based on properly conducted field density and laboratory Proctor tests.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Compaction acceptance must follow the project specification and be based on properly conducted field density and laboratory Proctor tests.

Frequently Asked Questions

How is the Soil Compaction figure worked out?

RC = field dry density / maximum dry density x 100. Relative compaction is field dry density divided by the maximum dry density obtained in a Proctor test, expressed as a percentage.

Why can compaction exceed 100 percent?

Because the reference is the standard Proctor maximum. Modified Proctor energy or heavy field rollers can exceed it, so values of 100-104 percent of standard are common and acceptable.

What values do I need to enter?

This calculator takes 3 inputs: Field dry density, Maximum dry density from Proctor, Specified compaction. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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