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Free online excavation calculator

An excavation calculator converts dig dimensions into cubic yards and dump truck count. It applies soil swell factors — clay 35%, loam 25%, sand 12%, rock 50% — so hauling.

About this calculator

How to use

  1. Enter the length and width of the excavation in feet.
  2. Enter the depth in feet (divide inches by 12 if needed).
  3. Select the soil type — this sets the swell factor automatically.
  4. Click Calculate.
  5. Read bank volume (undisturbed soil), loose volume (what trucks carry), and truck count.

Formulas

area (sq ft)          = length × width

bank volume (cu yd)   = length × width × depth / 27

swell factors:
  clay  = 35%
  loam  = 25%
  sand  = 12%
  rock  = 50%

loose volume (cu yd)  = bank volume × (1 + swell factor)

trucks needed         = ceil(loose volume / 10)

Worked example

Foundation for a 20 × 20 ft building pad, 4 ft deep, loam soil:

area               = 20 × 20 = 400 sq ft

bank volume        = 20 × 20 × 4 / 27
                   = 1,600 / 27
                   ≈ 59.26 cu yd

loose volume       = 59.26 × 1.25
                   ≈ 74.07 cu yd

trucks needed      = ceil(74.07 / 10) = 8 trucks

Notes

  • Always add one extra truck to your order as a buffer. Soil weight and volume vary.
  • Rock is highly variable — get a geotechnical report for large commercial cuts.
  • Loose volume is what you haul. Bank volume is what you fill. They are not interchangeable without applying the swell or shrinkage factor.

Frequently asked

What is a swell factor in excavation?
When soil is excavated it loosens and expands. A swell factor is the percentage increase in volume. Clay swells roughly 35%, loam 25%, sand 12%, and blasted rock 50%. You must account for swell when estimating hauling costs because trucks carry loose volume, not bank volume.
What is bank volume versus loose volume?
Bank volume (BCM — bank cubic measure) is the volume of soil in its undisturbed, in-ground state. Loose volume (LCM) is what that same soil occupies after excavation. Loose volume = bank volume × (1 + swell factor).
How many cubic yards does a dump truck hold?
A standard tandem-axle dump truck holds about 10 cubic yards of loose soil. Larger tri-axle trucks can carry 12–14 cubic yards. This calculator uses 10 cubic yards as a conservative default.
How do I calculate excavation volume?
Bank volume (cu yd) = length (ft) × width (ft) × depth (ft) ÷ 27. Then multiply by (1 + swell factor) to get the loose volume you will need to haul away.
Does the calculator account for fill material?
Fill material uses bank volume — you need the same bank volume of borrow material to fill the excavation (assuming similar compaction). The calculator shows bank volume for this purpose.
How do I share my excavation calculation?
Click Share to copy the page link, or Share with my numbers to include your dimensions in the URL so others can see the same result.

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