Compaction Calculator
Order the right amount of fill: enter the area and the compacted depth the spec calls for, and the calculator returns the loose volume to buy — applying both the swell the material carries on the truck and the shrink it gives up under the compactor. With the common-earth defaults that is roughly 1.39 loose yards per compacted yard in place, which is why ordering one-for-one against the compacted quantity comes up short. It also counts lifts at your lift depth. Free, no login.
Fill Placement
Material
Loose order = compacted × (1 + 25% swell) ÷ (1 − 10% shrink). Place in 8" lifts. Typical planning figures — swell 25% (typ 15–30%), shrink 10% (typ 5–15%); confirm with a geotech.
How this calculator works
Both conversion factors are measured against bank (in-place) volume: loose = bank × (1 + swell) and compacted = bank × (1 − shrink). Chaining them gives the loose volume that places a target compacted volume — the dimensionally-correct path, not a single fudge factor:
loose = compacted × (1 + swell%) ÷ (1 − shrink%) · lifts = ⌈compacted depth ÷ lift depth⌉
Swell and shrink are separate physical effects and both apply when you buy loose material to place compacted fill. They are also ranged, empirical properties — the presets are typical planning figures (typ 5–40% swell and 0–20% shrink across these classes), and the real numbers move with material, moisture, and the compaction spec. The geotech report or a test on the actual borrow material governs; field density tests prove compliance, not a calculator.
Worked example
A 2,000 ft² pad needs 12" of compacted common-earth fill, placed in 8" lifts:
- Compacted in place: 2,000 × 1 ft = 2,000 ft³ ÷ 27 = 74.07 yd³.
- Loose to order: 74.07 × 1.25 ÷ 0.90 = 102.88 yd³ — about 39% more than the compacted quantity.
- Lifts: 12 ÷ 8 = 1.5 → 2 lifts (lift counts round up; the spec and compactor manual set the allowable lift depth).
Enter the same fill above (2,000 ft², 12" compacted, common earth, 8" lift) to reproduce it.
Reference: loose yards per compacted yard by soil class
The order factor at each soil class’s default swell/shrink, computed by the same engine — with the typical ranges that make clear these are planning figures, not constants. Confirm with a geotech for a specific borrow source.
| Soil class | Swell (typ range) | Shrink (typ range) | Loose per compacted yd³ |
|---|---|---|---|
| Sand / gravel | 12% (5–18%) | 12% (8–15%) | 1.27 yd³ |
| Common earth / loam | 25% (15–30%) | 10% (5–15%) | 1.39 yd³ |
| Clay | 30% (20–40%) | 10% (5–20%) | 1.44 yd³ |
| Rock (blasted) | 50% (40–65%) | 0% (0–5%) | 1.50 yd³ |
Blasted rock carries 0% shrink deliberately: shot rock swells 40–65% and never compacts back below its bank volume — the voids between fragments cannot be squeezed out the way soil voids can.
Frequently asked questions
How much loose fill do I need to order for a compacted volume?
More than the compacted volume — typically 25–45% more for soils at this calculator’s default factors. Trucks deliver loose yards, and that material has to give back its swell and then compact below bank density, so the calculator orders loose = compacted × (1 + swell) ÷ (1 − shrink). With the common-earth defaults (25% swell, 10% shrink) that works out to about 1.39 loose yards per compacted yard in place. Ordering fill one-for-one against the compacted quantity is the classic way to come up short.
What is the difference between swell and shrink factors?
Both are measured against bank (in-place) volume. Swell is how much the volume grows when soil is excavated or dumped loose — bank to loose. Shrink is how far the compacted volume ends up below bank — bank to compacted. They are separate physical effects, and both apply when you buy loose material to place compacted fill, which is why this calculator uses both factors together.
What lift thickness should I use when placing fill?
Around 8 inches loose is a common general-fill spec for a ride-on roller, tightening to 6 inches or less for hand-operated compactors and cohesive soils — but the project spec and the compactor manufacturer govern, so use their number here. This calculator divides your lift depth into the compacted fill depth to count lifts. Thinner lifts compact more reliably; failing density tests on thick lifts costs more than the extra passes.
What compaction percentage do specs usually require?
Most specs require a percentage of maximum dry density from a Proctor test — commonly 90–95% of standard Proctor (ASTM D698) for general fill and 95% or higher under slabs, footings, and pavement, with modified Proctor (ASTM D1557) specified on heavier work. The exact number, test method, and moisture window come from the project spec and geotech report. Field density tests prove compliance; no calculator does.
Does compacted rock take up less volume than it did in the ground?
No. Blasted rock swells 40–65% when shot and never compacts back below its bank volume — the voids between rock fragments cannot be squeezed out the way soil voids can. That is why this calculator carries 0% shrink for blasted rock: a bank yard of rock always places as a yard or more of fill. There is no shrink to claw back when budgeting rock fill.
Method: compacted volume from area × depth ÷ 27, then loose = compacted × (1 + swell) ÷ (1 − shrink) — both factors referenced to bank volume, applied together. Swell and shrink percentages are typical planning ranges, not measured values; the project spec sets the required density (commonly a percentage of Proctor maximum dry density per ASTM D698 or D1557) and the geotech report governs the factors. Lift depth is a spec/compactor value — around 8" loose is a common general-fill figure, tighter for hand compactors and cohesive soils — and field density tests, not this calculator, prove compliance.
Pair with the Soil Swell & Shrink Calculator for the raw state conversions, the Cut & Fill Calculator to balance the site that generates the fill demand, or the soil moisture reference and BCY/LCY/CCY conversions chart for the Proctor and volume-state background.