DIRT by SubTrack

Swell and shrink calculator

Bank, loose, and compacted are not the same cubic metre. Swell is how much the material grows when you dig it. Shrink is how much it loses when you compact it. Trucks haul loose. Pay quantities are often bank.

Formula

Loose = bank × (1 + swell). Compacted = bank × (1 − shrink). If you know loose, bank = loose / (1 + swell). Load factor is 1 / (1 + swell).

Worked example

100 bank m³ of common earth at 25% swell is 125 loose m³. At 12% shrink, compacted is 88 m³. A truck that holds 12 loose m³ needs about 11 loads, not 9.

Percent swell and shrink. Volume in m³ or yd³. Presets for sand, earth, clay, topsoil, and blasted rock.

Open the calculator

Field calculators

Estimates for bidding and the truck. Confirm against survey, geotech, and scale tickets before you price.

Swell & shrinkage

Soil changes volume as you dig and compact it. Enter a known volume in any state.

Material preset

Swell % (bank→loose)

Shrink % (bank→compacted)

Known volume

m³

Measured as

Bank (in-place)

100m³

Loose (haul / stockpile)

125m³

Compacted (placed)

88m³

Load factor

0.8

Multiply loose by this to get bank.

Swell and shrink calculator FAQ

What is the difference between bank and loose?

Bank is in-situ, in the ground. Loose is after excavation, in the truck or the pile. Loose is always larger than bank for soil and rock.

What swell factor should I use?

Sand and gravel are often near 12%, common earth near 25%, clay near 30%, blasted rock near 50%. These are typical ranges. Confirm with the cut and the scale ticket.

Why do my truck counts look low?

You probably divided bank volume by box size. Convert to loose first, then check payload weight. Wet clay hits the legal weight before the box is full.