## How to Calculate Bulking Factor for Earthworks Projects

Article By: Tom Ayre | Last Update: November 2020

Calculating bulking factors are an important element in earthworks projects. Knowing the volume of material after an excavation has taken place is important because:

- Calculating accurate costs for removing material.
- Working out how and where to store the material.
- Factoring in the right amount of time to deal with the material.

In this blog article I will explain how bulking factors work, how to calculate by hand and give you a free to use calculator tool that will help with:

- Calculating bulking factor volume
- Calculating how many trips to remove the material
- Calculating how much storage you need.

Let’s get started!

## A Brief Introduction to Bulking Factors

To use a bulking factor number you have to multiply the bulking factor number by the excavated volume size.

For instance, a bulking factor for Clay and Gravel is typically 1.15

If your excavation was 15 m3.

Your volume size would be 1.15 x 15 = 17.25 m3

You must consider the bulking factor of the material you are digging to ensure you correctly plan for the removal costs and time to do it in.

## Diggability Factors

Each material that you excavate will have different properties in terms of how easy they are to dig.

The most common way of categorising a soils digability or ease of digging is:

E = Easy digging – Loose free-running soils eg sands, fine gravels.

M = Medium – Denser cohesive soils eg clayey gravel, low PI clays

M-H = Medium to Hard – eg broken rock, wet heavy clay, gravel with boulders

H = Hard – material requiring blasting and hard high PI clays

In our calculator below, you will see the materials digability using the “E”, “M”, “M-H”,”H” format.

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## Earth Movement / Bulking Calculator

Use this form to:

- Calculate bulked out volume
- Calculate how many trips to remove the material.
- Calculate how many storage units to store the material.

## How To Calculate Volume Size

**Rectangular Excavation**

Volume = W x H X L

Example = 1.5 x 2 x 8

= 24 m3

**Cutting Excavation**

Volume = ((H * W1) / 2) + (W2 * H) + ((H * W2) / 2)) * L

Example = ((0.5 * 0.3) / 2) + (1.5 * 0.5) + ((0.5 * 0.3) / 2)) * 2.1

= 1.89 m3

## References

References: https://community.dur.ac.uk/~des0www4/cal/roads/earthwk/earthwk.html