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Septic & DrainageCalculators

Earthwork

Excavation Volume Calculator

Size a dig before you start. Enter rectangular or circular dimensions to get the in-place volume, then apply a swell allowance to see the loose volume you will actually be hauling or stockpiling.

Your measurements

Results update as you type. Every unit dropdown converts for you.

%

Soil takes up more room once dug. Set to 0 to skip it.

In-place volume

17.78cubic yards

Loose volume after swellWhat you haul or stockpile
22.22 cu yd
In-place volume in cubic feet
480.0 cu ft
In-place volume in cubic meters
13.59 m³
Loose volume in cubic feet
600.0 cu ft
Swell allowance used
25%
Show the calculationOpen
  1. In-place volume12.00 ft × 8.00 ft × 5.00 ft=480.0 cu ft
  2. Convert to cubic yards480.0 ÷ 27=17.78 cu yd
  3. Apply swell17.78 × (1 + 25 ÷ 100)=22.22 cu yd

Reading your result

In-place volume is the size of the hole. Loose volume is what comes out of it once the soil breaks up and traps air, and that is the figure that fills trucks and stockpiles.

Use in-place volume to understand the dig and loose volume to plan haulage. Quoting one when the contractor meant the other is a common source of surprise on the invoice.

For backfill, neither figure is quite right on its own — material compacts as it goes back, so replacing an excavation usually takes more than the in-place volume suggests.

How this calculator works

In-place volume is the size of the hole: length times width times depth for a rectangular dig, or π times radius squared times depth for a circular one.

Loose volume is larger. Digging breaks up soil structure and traps air, so the same material takes up more room in a truck or a pile than it did in the ground. That increase is called swell, and it is entered as a percentage.

Swell varies with material. Sand and gravel expand relatively little; dense clay expands more. If you are ordering haulage, the loose figure is the one that fills the truck.

Backfill works the reverse way. Material compacts as it goes back in, so replacing an excavation generally needs more imported material than the in-place volume suggests.

The formula

Rectangular volume
length × width × depth
Circular volume
π × radius² × depth
Cubic yards
cubic feet ÷ 27
Loose volume
in-place volume × (1 + swell ÷ 100)

Worked example

A rectangular excavation 12 ft by 8 ft by 5 ft deep, with a 25% swell allowance.

  1. 01In-place volume12 × 8 × 5=480 cu ft
  2. 02Cubic yards480 ÷ 27=17.78 cu yd
  3. 03Apply swell17.78 × 1.25=22.22 cu yd
  4. 04Cubic meters in place480 × 0.0283168=13.59 m³

The hole is about 17.8 cubic yards, but you will be moving roughly 22.2 cubic yards of loose material.

How to take the measurements

  • Measure the dig at its full extent, including any working room beyond the structure itself.
  • Take depth from existing grade, not from finished grade, if the site is going to be regraded afterwards.
  • For a circular dig, measure the diameter across the widest point of the excavation, not the diameter of the tank or structure going in.
  • Set swell from the material you expect: lower for sand and gravel, higher for dense clay.
  • Where soil is layered, calculate each layer separately if the swell characteristics differ meaningfully between them.

Practical considerations

  • Haulage is usually priced by the load, so the loose figure translates directly into cost. Knowing it before you book avoids a second trip.
  • Stockpiling on site avoids haulage but needs somewhere the pile can sit for weeks without smothering plantings or blocking access.
  • Reusing excavated material as backfill only works if it is suitable. Topsoil, rubble and saturated clay generally are not.
  • Have utilities located before any dig. The service is free in most areas and required in many.

Assumptions and limitations

  • The calculation assumes vertical sides. Battered, benched or shored excavations hold more volume than the nominal dimensions.
  • Swell is a single percentage applied uniformly. Layered ground with different materials will not behave that way.
  • Nothing here determines whether an excavation can be carried out safely, what shoring it needs, or what depth triggers additional requirements.

Frequently asked questions

What is soil swell?

The increase in volume when soil is dug. Loose material contains voids that were not there in undisturbed ground, so the same weight of soil occupies more space once excavated.

How much swell should I allow?

It depends on the material. Sand and gravel expand least, common earth falls in the middle, and dense clay expands most. Twenty-five percent is a reasonable placeholder for mixed soils, but material-specific figures are better if you have them.

Do I use in-place or loose volume for hauling?

Loose. Truck capacity is a volume, and what goes in the truck is loose material.

How much backfill will I need?

More than the in-place volume, because backfill compacts as it is placed. Work from the void you need to fill and add an allowance based on how the material will be compacted.

Do I use in-place or loose volume for hauling?

Loose. Truck capacity is a volume, and what goes in the truck is loose material.

How much swell should I allow?

It depends on the material. Sand and gravel expand least, dense clay most. Twenty-five percent is a reasonable placeholder for mixed soils if you have nothing better.

Why does the hole look bigger than the numbers?

Because excavations are rarely dug to exact dimensions, and sides that batter outward add volume quickly with depth.

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