Free online excavation 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.