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One of the most important factors when choosing bulk bags is how much they can hold. You need an accurate calculation of volume to be able to establish how many bulk bags you’ll need to move your material from one place to another. A simple length x width x height calculation may not always yield accurate results.

There are many volume calculators available online that claim to take into consideration certain factors that can affect volume calculations, but the fact remains that every bulk bag is slightly different in design and modifications. Certain optional extras can increase or decrease the usable volume. The bulk density of your material also plays a large role in usable volume.

You need to factor in all of these variables in order to correctly assess how many bulk bags to order. Your supplier will be able to help you with these calculations. Custom Bulk Bags is a leading manufacturer and supplier of bulk bags in South Africa. We offer consultations and guidance to our customers that will help them to choose the perfect packaging products for their needs.

Why volume sums are critical?

When dealing with large quantities of material, even small differences in the actual volume of the packaging can make a big difference to logistics and storage requirements. If you fail to correctly calculate the volume of material that your bulk bags can hold, then you could end up with leftover material that doesn’t fit into the bags or too many bags left in stock. 

These calculations also let you estimate how much room you need for storage or how many shipping containers to fill. Errors can lead to costly misjudgement which will affect your bottom line. Your volume calculations influence shipping, storage and ordering decisions, so it’s crucial to get right.

Choosing between coated and uncoated bulk bags

What can affect volume calculations?

  1. Bulk density – The first factor to consider is the bulk density of your material. This is how coarse or fine the substance is. For example, mining ore and rubble had large air spaces in between the grains, which takes up volume. Powders, sugar and fertilizer have a much finer grain, which means fewer air pockets and an increased usable volume of the bulk bag.
  1. Optional extras – You need to consider what optional extras are included on your bulk bags. These can alter the shape of the bag, so a length x width x height calculation becomes irrelevant. Filling and discharge spouts can slightly increase the usable volume, whereas inner liners and baffles can slightly decrease their capacity.
  1. Construction of the bags – The type of materials and the construction of the bags influence their volume. Bulk bags with foil liners, baffles and sift-proof seams are slightly more rigid. On the other hand, a simple bag with no optional extras may be more flexible and able to hold slightly more as it stretches. This is known as ‘rounding’, which means that a cylindrical volume calculation may be more accurate (V=πr2h).
  1. Lifting loops – The loop design can also influence volume calculations, but not in the way you may think. Loops determine how much clearance you have under your filling equipment and forklifts. Longer loops allow for more space, but they also require the bag to be shorter, which impacts volume. Shorter loops allow for taller bags to fit underneath filling equipment, so speak to your supplier about their recommendations.

When you’re buying bulk bags, you need to be sure that they will be able to hold all of your material with no waste. Consider all of the above factors before placing an order and spend some time doing volume calculations. Alternatively, speak to an expert at Custom Bulk Bags for assistance.

Avoid unintended mishaps and ensure that you have enough bulk bags to store and transport your materials. For more information about our bulk bags or for guidance with your volume calculations, please contact us today.


Custom Bulk Bags is a leading South African manufacturer of woven polypropylene bags for various industries, such as mining, chemicals and food. We are able to produce over 3.5-million bulk bags per year, keeping our customers in stock at all times. Our bags adhere to the highest levels of quality as a result of our stringent in-house testing and quality control programmes.

Custom Bulk Bags holds ISO 9001 certification and we currently have a number of UN-certified designs. We are a Level 2 B-BBEE manufacturer and supplier and fall under the ownership structure of Deneb Investments Limited. For more information on our products, contact Follow us on Facebook for our latest news and industry insights.