Excavation Swell Calculator: Bank to Loose Volume and Truck Loads

Bank, Loose, and Compacted Volume

Explanation

Excavation volume estimation is more than length x width x depth. Soil expands when it is excavated because particles loosen and trap air. This expansion is called swell, and it is a major driver of hauling costs. Bank volume refers to the in-place volume of soil before excavation. Loose volume refers to the excavated material after it has expanded. Knowing both values is essential for material estimation and truck logistics in precision building projects.

The swell factor depends on material type, particle size, excavation method, and moisture content. Published bulking-factor tables often show broad ranges, such as 20 to 40 percent for clay, 20 to 30 percent for sand or gravel, and much higher values for blasted rock. This calculator applies your selected or custom swell percentage to the bank volume to calculate loose volume. Once loose volume is known, the tool divides by truck capacity and rounds up to ensure you order enough trips. Rounding up is important because partial loads still incur mobilization costs and time on site.

This tool supports imperial and metric units, which allows you to work in feet and cubic yards or meters and cubic meters. It is a planning tool for excavation bids and scheduling, not a substitute for geotechnical investigation. Swell varies by soil classification and compaction state, so field verification is still required for critical earthwork or load-bearing foundations. Use this estimator as a realistic baseline for hauling, staging, and disposal planning.

Moisture content changes swell behavior. Wet clay can swell differently than dry clay, and sandy soils can settle quickly once disturbed. If you are excavating for backfill, you may need to apply a shrink factor to estimate compacted volume, which is separate from swell. In practice, contractors often track both loose and compacted volumes to avoid shortages or surplus trucking. Document assumptions for bids and compare against actual haul tickets.

Typical Swell Factors

Use these as planning ranges for bank-to-loose volume conversion. They are reference-style estimating values based on common earthwork practice and published bulking-factor tables; project specifications, geotechnical reports, DOT tables, or measured truck tickets should override generic assumptions.

Soil texture, clay minerals, moisture, and particle size distribution affect field behavior. Range examples are adapted from published soil and rock bulk-factor references such as Engineering ToolBox soil and rock bulk factors. For formal bids, cite the project specification or geotechnical basis for the swell factor you enter.

Formula

Bank volume: Vb = L x W x D

Imperial conversion: bank yd3 = bank ft3 / 27

Loose volume: Vl = Vb x (1 + swell)

Volume-limited loads: loads = ceil(Vl / truck capacity)

Estimated weight: weight = loose volume x density

Payload-limited loads: loads = ceil(weight / payload limit)

Compacted backfill volume: Vc = Vb x (1 - shrink)

Worked Examples

FAQs

What is the difference between bank cubic yards and loose cubic yards?

Bank cubic yards are measured before excavation while the material is still in place. Loose cubic yards are measured after digging, when the same material occupies more space because of swell.

What swell factor should I use for clay or sand?

A planning range of about 20 to 40 percent is common for clay, while dry or wet sand is often shown around 20 to 30 percent in published bulking-factor tables. Use project specifications or geotechnical data when available.

How many cubic yards fit in a dump truck?

Small dump trucks may carry about 5 to 7 cubic yards, tandem trucks often carry around 10 to 15 cubic yards, and larger trucks can carry more. Payload weight and local road limits can reduce the usable volume.

Why does the calculator round up loads?

The calculator rounds up because a partial final load still requires a truck trip. Exact loads show the mathematical division before rounding.

How should I handle multiple soil layers?

Run each soil layer separately with its own dimensions, swell factor, and density, then add the loose volumes, weights, and truck loads.

Does moisture change the swell factor?

Yes. Moisture changes density, cohesion, handling behavior, and how much void space develops after excavation. Wet and dry material presets should be treated as planning assumptions.

Should excavation volume be measured before or after digging?

Measure the cut dimensions before digging to get bank volume, then apply swell to estimate loose hauled volume. Haul tickets and disposal records usually reflect the loose or payload-limited result.

Can this estimate compacted backfill volume?

Yes. Turn on compacted backfill mode to apply a shrink factor to bank volume. This is separate from loose swell and should be checked against compaction specifications.

How it works

This tool applies an editable swell percentage to bank volume, divides loose volume by truck capacity, and optionally compares the result with payload-limited trips from density and weight. All calculations run client-side.

Disclaimer

Results are estimates. Soil conditions vary, and hauling requirements should be verified against site data and local regulations.