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Bulk Bag Volume Calculators: What to Look For

Posted by Sonoco Conitex Team on December 19,2022

If you think about it, the most fundamental thing you need to know about a bulk bag is how much it’s able to carry. 

Not all bags (not even bags that technically have the same approximate size and shape) are equal. Not all bag volume calculators can be trusted for accuracy. The different ways you modify your bulk bags, the type of product you’re filling your bag with, the stretchiness of the type of fabric used, and even the way that you fill your bags all affect your bag’s fillable volume. When you factor in the unique characteristics of your product, it becomes clear that you need a bag that’s specifically designed to support your precise needs. 


When you’re dealing with a product in bulk, even minute differences in estimated or actual volume can make a huge difference. Imagine not having enough room to store your valuable product or failing to ship as much as you could because you underestimated capacity or used a faulty bag volume calculation.

Your bag’s volume influences your shipping and storage decisions and relates to the type of product you’re able to use with your bags. Understanding your bag’s capacity will also help you know how many bags you’ll need for your specific circumstances. 

Ultimately, understanding how to navigate bag volume can save you a lot of money, frustration, and potential risk. Let’s dive into bulk bag volume calculation. 

Your Bulk Bag’s Design and Its Usable Volume

As you and your flexible intermediate bulk container (FIBC) manufacturer design a bag that will work well for you, it’s key to get the specifications and dimensions of your bulk bag right. Here’s a quick overview of the terms that may come up in that conversation: 

  • Bag Height: A bag’s height is measured from the top seam to the bottom seam. 

  • Volume: A bulk bag’s volume refers to the size or amount of material that an FIBC can hold. Generally, this measurement will be reported in cubic feet. 

  • Safety Factor: A bag’s safety factor refers to the amount of load a bag has been proven to safely handle. It’s an industry standard that an FIBC should be able to handle five or six times its safe working load.

In general, a bulk bag can follow the basic formula for cylindrical volume (V=πr2h, where r is the radius of the cylinder and h is its height). More structured bags (such as baffle bags) require a different bag volume calculation. They follow the basic formula for the volume of a cube: volume equals length times width times height. Under this formula, a 35-inch by 35-inch by 35-inch bag can hold a minimum of 42,875 cubic inches, or 25 cubic feet, of material. Bags with larger dimensions offer increased capacity.

Your Product, Its Bulk Density, and Your Bulk Bags

Your product’s specific bulk density has a strong connection to the amount of your product that will fit in each of your FIBCs. 

When you’re purchasing bulk bags, the materials scientists at your FIBC manufacturer will use your bulk density—and other relevant data, such as the size of pallets you’re working with—to determine the specifications of FIBC that will work best for you. Before you place your order, make sure you know your product’s bulk density and how many pounds of product you need to support, and you’ll be well on your way to selecting a bag capacity that will work well for your processes. 

There are many bulk bag suppliers in the U.S., so it can be hard to determine  which provide the game-changing services, expertise, and reliability you need.  Luckily we've put together this full guide on what to look for in your FBIC  supplier. 

Real-Life Factors Affecting Bulk Bag Capacity

After you’ve done the math to determine your bag’s usable volume and your product’s bulk density, your job isn’t quite done. These factors could affect how your product fills your bag: 


Think about a bag with a structured square bottom. A very short bag is going to retain that square shape. On the other hand, if your bag is extremely tall, it’s going to round until it looks more like a cylinder—even though it has that same square base. This will influence the type of calculation you’re going to need to use to estimate the volume of that particular bag. 

Inlet Type

Your FIBC’s inlet type is the type of spout or top that you choose to match your filling mechanism. Different inlet types (for example, conical tops) affect your bag’s capacity in different ways. 

Bulk Bag Lift Loops

The lifting loops you select for your bag play a role in your clearance under your filling equipment since this affects the overall size of the bag. The industry standard for lift loops is 10 inches. When you require longer loops, your bag needs additional clearance, which means the bag itself will need to be smaller. 

Good news: The materials scientists at your bag manufacturer will be able to help you with each of these considerations. That’s why you go to the bulk bag experts to make sure you have the right FIBCs for your specific situation. 

Conitex Sonoco Is Ready to Assist with Complex Calculations and More! 

When you’re purchasing a bulk bag that’s going to go the distance for you and your company, you need to know that it’s going to be physically capable of doing the job. Your unique product’s bulk density, the amount of product you need to move, and the capacity of your intended bag all need to be perfectly aligned. Otherwise, you may face an unintended disaster scenario in the warehouse or while your product is en route! 

The materials scientists and FIBC experts at Conitex Sonoco are ready to give you confidence in your bags’ capacity to perform. (We’ve got the calculations; we can show our work!) Got a question about FIBC safety? Give our friendly, knowledgeable team a call. We’ll be able to get you the answers and high-quality products that you need.

Download our ebook: Vetting Bulk Bag Vendors

Tags: FIBC Bulk Bags, bulk bags

Sonoco Conitex Team

Sonoco Conitex Team