Bank Cubic Feet Calculator: Volume & Swell

This calculator converts between bank cubic feet (BCF), loose cubic feet (LCF), and compacted cubic feet (CCF) using swell and shrinkage factors. You enter the volume in one state and the applicable percentage, and it returns the equivalent volumes in the other two states, helping you plan earthmoving and excavation projects accurately.

Formula

The core relationships are:

• Loose volume = Bank volume × (1 + Swell% / 100)
• Compacted volume = Bank volume × (1 − Shrink% / 100)

Where:

• Bank volume – the volume of material in its natural, undisturbed state (in cubic feet, cubic yards, or cubic meters).
• Swell % – the percentage increase in volume when material is excavated and becomes loose (e.g., 25% for common earth).
• Shrink % – the percentage decrease in volume when material is compacted (e.g., 10% for clay).

All volumes must be in the same unit. The calculator uses cubic feet, but you can convert to cubic yards by dividing by 27.

Worked Example

Using the default values: Bank volume = 1000 cu ft, Swell = 25%, Shrink = 10%.

1. Loose volume = 1000 × (1 + 25/100) = 1000 × 1.25 = 1250 cu ft
2. Compacted volume = 1000 × (1 − 10/100) = 1000 × 0.90 = 900 cu ft

So 1000 bank cubic feet of earth becomes 1250 loose cubic feet when excavated, and 900 compacted cubic feet after compaction. These are the results shown by the calculator.

Why Bank Cubic Feet Matter

In construction, mining, and landscaping, materials are measured in three states: bank (in place), loose (after digging), and compacted (after being tamped down). A cubic yard of soil in the ground does not occupy the same space once it is loaded into a truck – it expands. Understanding this prevents over-ordering or under-ordering fill, and helps estimate trucking needs.

For example, if you need to move 10,000 bank cubic yards of rock, you must know that it will swell to about 15,000 loose cubic yards in haul trucks. That affects the number of loads and the cost. Conversely, if you are building a road embankment that requires 5,000 compacted cubic yards, you need to source more than 5,000 bank cubic yards to account for shrinkage during compaction.

How to Use the Calculator

Enter the volume you know in the “Volume� field – typically the bank volume, but you can also use it to convert from loose or compacted by adjusting the formula. The calculator assumes the input is bank volume. If you have loose volume, you can divide by (1 + swell/100) to get bank volume, then use that as input.

Set the swell percentage for your material. Common values:

• Clay (dry) – 25% to 35%
• Earth (common) – 20% to 30%
• Sand – 10% to 15%
• Gravel – 10% to 20%
• Rock (blasted) – 30% to 50%

Set the shrink percentage (typically 5% to 15% for soil). If you don’t know it, use 10% as a starting point, but check local geotechnical data.

Common Mistakes and Misconceptions

A frequent error is mixing up swell and shrinkage percentages. Swell is always an increase from bank to loose; shrinkage is a decrease from bank to compacted. They are not additive – you cannot simply add 25% and 10% to get a net change. The correct approach is to apply each factor to the bank volume independently.

Another mistake is using the wrong unit. The calculator uses cubic feet, but many projects quote cubic yards. Remember: 1 cubic yard = 27 cubic feet. If you enter 1000 cubic yards, you must convert to cubic feet first (27,000 cu ft) or the result will be off by a factor of 27.

Also, swelling and shrinkage are not exact – they vary with moisture, compaction effort, and material type. Always use a range and plan for uncertainty. For critical projects, a geotechnical engineer should provide the actual factors.

Limitations of the Formula

The simple percentage method assumes a uniform material and a linear relationship. In reality, swell and shrink can be non-linear, especially for mixed soils or when compaction is done in layers. The formula also does not account for moisture changes, which can cause volume changes beyond mechanical swelling.

For large earthmoving projects, more sophisticated methods (like soil compaction curves) are used. But for most small to medium tasks, the percentage approach is accurate enough for budgeting and logistics.

Frequently Asked Questions

What is a bank cubic yard?

A bank cubic yard (BCY) is a unit of volume representing one cubic yard of material in its natural, undisturbed state, as it exists in the ground. It is the standard measure for estimating excavation quantities.

How do I convert bank cubic feet to cubic yards?

Divide the volume in cubic feet by 27. For example, 1000 bank cubic feet is 1000/27 ≈ 37.04 cubic yards. The calculator gives results in cubic feet, so you can do this conversion manually if needed.

What is the typical swell factor for topsoil?

Topsoil usually swells by about 20% to 30% when excavated. This means 100 bank cubic yards of topsoil will become 120 to 130 loose cubic yards. The exact value depends on moisture and organic content.

Can I use this calculator for rock?

Yes, but rock swell factors are higher, often 30% to 50% for blasted rock. The calculator works the same way; just enter the appropriate swell percentage for your material.

Why does compacted volume sometimes show a negative number?

That happens if you enter a shrink percentage greater than 100%. Shrink percentages are always less than 100% in practice, so double-check your input. The calculator allows any number, but realistic values are between 0 and 50%.

Alternatives and Related Measurements

If you work in metric, the same relationships apply to cubic meters. The calculator uses feet, but you can convert inputs to feet and then convert outputs back. For trucking, you might need to know the density of the material to estimate weight, which is a separate calculation.

Another related concept is the “load factor� used in mining, which is the ratio of loose density to bank density. This is equivalent to 1/(1 + swell/100). The calculator effectively uses that factor.

Related

• Adding Pounds and Ounces Calculator: How It Works
• 57 7 Inches to Fraction Calculator and Conversion Guide
• 1 Inch to Inches Calculator and Conversion Explained

in v | Volume | cu ft | 1000 | 0
in swell | Swell % | % | 25 | 0
in shrink | Shrink % | % | 10 | 0
out loose | Loose volume | cu ft | v * (1 + swell/100) | 2
out compacted | Compacted volume | cu ft | v * (1 - shrink/100) | 2
out bank_equiv | Bank from loose | cu ft | (v * (1 + swell/100)) / (1 + swell/100) | 2