There’s a reason why FIBC bulk bags are a fundamental part of so many industries. Any sector that deals with bulk materials can yield significant cost savings by using bulk bags, with these heavy-duty flexible containers able to handle significant loads. However, choosing the right bag size can be difficult for new businesses or established enterprises looking to expand their operations.
The good news is that you can take the hard work of FIBC bag calculation with an FIBC calculator. These handy tools make calculating FIBC bag dimensions a breeze, ensuring you’re never with containers that aren’t fit for purpose.
There are many reasons why you should be using an FIBC bag dimension tool when selecting flexible containers for your business. For starters, calculators make quick work of FIBC bag dimension selection. If you’re thinking of improving packaging solutions with FIBC calculators, these tools will ensure any container you choose can handle the weight of the materials you’re using. Further benefits of FIBC bag calculators include safe handling as standard and a guarantee that products are protected in transit.
Selecting the perfect bag dimensions is easy when you use an FIBC calculator. Although there might be some variation between calculators between different suppliers, most follow the same basic principle.
To start with, you’ll need to think about the materials you’re looking to store and transport in FIBCs. You’ll need to determine the overall volume of the product before you can choose a suitable bulk bag. To find the volume, simply divide the overall weight of your product by its bulk density. While an FIBC calculator will take care of the equation for you, you might not be familiar with individual bulk densities of common materials. To make life easier, it’s worth checking out the average densities of the materials you’re dealing with. There’s a lot of variation here, so don’t rely on guesswork. Once you have the right bulk density to value at hand, you can input it into an FIBC calculator along with the product weight to find the product volume in cubic feet.
Next, you can focus on the actual dimensions of your FIBC bags. Many suppliers offer basic square-shaped FIBCs with a base measuring 35 inches along each side. However, you’re free to go larger if these bulk bags are too small for your requirements. Before selecting a larger bag, consider the rest of your production line. If you’re currently using pallets, ensure bulk bag dimensions are compatible with them. Once you’ve decided on bulk bag dimensions, an FIBC calculator will provide you with a revised estimate of bulk bag capacity.
Sizing an FIBC comes down to two calculations. The first converts the weight of your product into the volume it will occupy. The second converts that volume into a bag height for a given base size.
Step 1. Find the volume of your product
Volume (ft³) = Product weight (lb) ÷ Bulk density (lb/ft³)
Volume (m³) = Product weight (kg) ÷ Bulk density (kg/m³)
Step 2. Find the bag height
Bag height = Volume ÷ Base area
For a standard 35 in × 35 in base, the base area is 8.51 ft² (0.79 m²). A product volume of 30 ft³ therefore needs a fill height of 30 ÷ 8.51 = 3.53 ft, or roughly 42 in, before headroom is added. Add 10 to 15 per cent to the calculated height so the bag is not filled to the seam.
Always check the result against the safe working load. Volume determines how much product physically fits. Safe working load (SWL) is a separate structural rating. A 1,000 litre bag filled with a dense mineral can exceed its SWL long before it is full.
Bulk density is the input most sizing errors come from. The figures below are typical loose bulk densities at standard handling moisture. Actual density shifts with moisture content, particle size and compaction, so for materials prone to variation, calculate using the higher end of the range. The suggested bag in each row is the standard size that carries a practical load of that material without exceeding a common safe working load.
| Material | Bulk density (lb/ft³) | Bulk density (kg/m³) | Typical FIBC size | Notes |
|---|---|---|---|---|
| Agriculture and food | ||||
| Wheat, whole grain | 48 | 770 | 35 × 35 × 50 in (1,005 L, approx. 775 kg fill) | Density varies up to 5 per cent with moisture. Ventilated bag preferred for storage. |
| Maize (corn), shelled | 45 | 720 | 35 × 35 × 55 in (1,105 L, approx. 795 kg fill) | Residual field moisture makes breathable fabric the safer choice. |
| Rice, milled white | 50 | 800 | 35 × 35 × 50 in (1,005 L, approx. 805 kg fill) | Food-grade bag with liner is standard for export. |
| Rice, rough (paddy) | 36 | 575 | 42 × 42 × 48 in (1,390 L, approx. 800 kg fill) | Substantially less dense than milled rice. Sizing from milled figures undersizes the bag. |
| Barley | 38 | 615 | 42 × 42 × 48 in (1,390 L, approx. 855 kg fill) | Volume-limited rather than weight-limited. |
| Oats | 26 | 415 | 42 × 42 × 48 in (1,390 L, approx. 575 kg fill) | One of the lowest-density grains. Bag volume, not SWL, sets the limit. |
| Soybeans | 47 | 750 | 35 × 35 × 50 in (1,005 L, approx. 755 kg fill) | Free-flowing, suits a discharge spout. |
| Wheat flour | 37 | 590 | 35 × 35 × 55 in (1,105 L, approx. 650 kg fill) | Fine powder. Requires sift-proof seams and a food-grade liner. |
| Granulated sugar | 53 | 850 | 35 × 35 × 50 in (1,005 L, approx. 855 kg fill) | Hygroscopic. Moisture barrier liner prevents caking. |
| Milk powder | 32 | 510 | 42 × 42 × 48 in (1,390 L, approx. 710 kg fill) | Food-grade, sift-proof construction with a sealed liner. |
| Animal feed pellets | 40 | 640 | 35 × 35 × 55 in (1,105 L, approx. 705 kg fill) | Density varies with pellet diameter and binder content. |
| Potatoes | 43 | 690 | 35 × 35 × 50 in (1,005 L, approx. 690 kg fill) | Ventilated bag essential to release residual field moisture. |
| Coffee beans, green | 42 | 675 | 35 × 35 × 50 in (1,005 L, approx. 680 kg fill) | Breathable fabric protects against condensation in transit. |
| Minerals and construction | ||||
| Sand, dry | 100 | 1,600 | 35 × 35 × 35 in (700 L, approx. 1,120 kg fill) | SWL-limited, not volume-limited. A 1,000 L bag would exceed most standard load ratings. |
| Silica sand | 100 | 1,600 | 35 × 35 × 35 in (700 L, approx. 1,120 kg fill) | Abrasive. Specify a heavier fabric weight and reinforced seams. |
| Gravel, dry | 95 | 1,520 | 35 × 35 × 35 in (700 L, approx. 1,065 kg fill) | Sharp aggregate. Consider a heavy-duty or double-walled bag. |
| Portland cement | 94 | 1,505 | 35 × 35 × 35 in (700 L, approx. 1,055 kg fill) | Fine powder plus high density. Coated fabric and a liner are both needed. |
| Limestone, crushed | 90 | 1,440 | 35 × 35 × 35 in (700 L, approx. 1,010 kg fill) | Density rises as particle size falls. |
| Rock salt, granular | 75 | 1,200 | 35 × 35 × 40 in (805 L, approx. 965 kg fill) | Highly hygroscopic and corrosive. Moisture barrier liner required. |
| Bentonite clay | 50 | 800 | 35 × 35 × 50 in (1,005 L, approx. 805 kg fill) | Swells on contact with moisture. Keep sealed. |
| Fly ash | 45 | 720 | 35 × 35 × 55 in (1,105 L, approx. 795 kg fill) | Extremely fine. Coated fabric with a sealed liner prevents sifting. |
| Chemicals and polymers | ||||
| PP or PE resin pellets | 35 | 560 | 42 × 42 × 48 in (1,390 L, approx. 780 kg fill) | Static build-up during filling. Specify a Type C or Type D antistatic bag. |
| Urea, prilled | 46 | 735 | 35 × 35 × 50 in (1,005 L, approx. 740 kg fill) | Hygroscopic and prone to caking. Moisture barrier essential. |
| NPK compound fertiliser | 60 | 960 | 35 × 35 × 45 in (905 L, approx. 865 kg fill) | Density varies widely by formulation. Confirm the figure with your supplier. |
| Soda ash, dense | 65 | 1,040 | 35 × 35 × 40 in (805 L, approx. 835 kg fill) | Light soda ash is roughly half this density. Confirm which grade you are shipping. |
| Calcium carbonate powder | 45 | 720 | 35 × 35 × 55 in (1,105 L, approx. 795 kg fill) | Fine powder. Sift-proof seams recommended. |
| Titanium dioxide | 40 | 640 | 42 × 42 × 48 in (1,390 L, approx. 890 kg fill) | Ultra-fine and high value. Sealed liner protects against loss and contamination. |
| Wood pellets | 40 | 640 | 35 × 35 × 55 in (1,105 L, approx. 705 kg fill) | Moisture-sensitive. Ventilated bag with weatherproof outdoor cover. |
Most FIBC production runs use a small set of standard base dimensions, with height as the variable. The chart below gives the volume and typical load rating for each, together with pallet compatibility. Safe working load is a structural specification set during manufacture, not a function of volume, so two bags of identical size can carry different rated loads.
| Dimensions (in) | Dimensions (cm) | Volume (ft³) | Volume (litres) | Typical SWL (kg) | Pallet compatibility |
|---|---|---|---|---|---|
| 31 × 31 × 43 | 79 × 79 × 109 | 23.9 | 675 | 500 to 1,000 | Euro pallet (800 × 1200 mm) |
| 31 × 31 × 51 | 79 × 79 × 130 | 28.4 | 805 | 500 to 1,000 | Euro pallet (800 × 1200 mm) |
| 35 × 35 × 35 | 89 × 89 × 89 | 24.8 | 700 | 1,000 to 1,500 | Standard 1000 × 1200 mm. Overhangs a Euro pallet. |
| 35 × 35 × 40 | 89 × 89 × 102 | 28.4 | 805 | 1,000 to 1,500 | Standard 1000 × 1200 mm |
| 35 × 35 × 45 | 89 × 89 × 114 | 31.9 | 905 | 1,000 to 1,500 | Standard 1000 × 1200 mm |
| 35 × 35 × 50 | 89 × 89 × 127 | 35.4 | 1,005 | 1,000 to 1,500 | Standard 1000 × 1200 mm. The most widely stocked size. |
| 35 × 35 × 55 | 89 × 89 × 140 | 39.0 | 1,105 | 1,000 to 1,500 | Standard 1000 × 1200 mm. Check container door height when loaded. |
| 35 × 35 × 60 | 89 × 89 × 152 | 42.5 | 1,205 | 1,000 to 1,500 | Standard 1000 × 1200 mm. Baffles recommended for stacking stability. |
| 36 × 36 × 36 | 91 × 91 × 91 | 27.0 | 765 | 1,000 to 1,500 | Standard 1000 × 1200 mm |
| 40 × 40 × 45 | 102 × 102 × 114 | 41.7 | 1,180 | 1,250 to 2,000 | 1200 × 1200 mm. Overhangs a 1000 × 1200 mm pallet. |
| 42 × 42 × 48 | 107 × 107 × 122 | 49.0 | 1,390 | 1,250 to 2,000 | 1200 × 1200 mm only |
Volumes are nominal and assume a filled bag with a square profile. A standard U-panel or circular FIBC bulges when filled, which increases the footprint and reduces the usable stack height. Baffle bags hold their shape and deliver closer to the nominal figure. Standard FIBCs carry a 5:1 safety factor; UN-certified single-trip bags carry 6:1.
Having a clear idea of product weight and bulk density is all well and good, but you need to remember that FIBCs are designed to be flexible. We offer FIBC bags for all kinds of industries; everything from the agricultural industry, to the chemical industry and the construction industry. Once filled, a standard FIBC may bulge at the sides. This can cause a problem if you’re worried about warehouse capacity or transport logistics. In other words, you may not be able to store as many FIBC bags as you initially thought. An easy way to get around this is to invest in baffled FIBCs. Thanks to their internal baffles, these bags are more robust than their everyday counterparts. As well as being more durable, they have less of a footprint, making them ideal for smaller warehouse facilities.
The same logic should be applied when considering the transportation of materials. If bulk bags can’t comfortably fit inside the back of a vehicle or carrier unit, the materials within can become compromised. To prevent tears, spillage, or contamination, it’s vital you choose FIBCs that are large enough to accommodate your materials when completely filled.
1. Can bulk density vary for the same material, and how does that affect calculator accuracy?
Yes, bulk density can shift based on moisture content, particle size, and storage conditions. To avoid undersizing, it’s best to calculate using the higher end of the density range for materials prone to variation.
2. How do filling and discharge methods influence which bag dimensions to choose?
Fill and discharge design affects how material settles inside the bag, which can impact usable capacity. These functional specifications should be factored in alongside volume calculations to avoid sizing mismatches in real-world use.
3. Does a calculated bag capacity also confirm the safe working load (SWL)?
Not automatically. Volume calculations determine physical capacity, but SWL is a separate structural specification. For dense materials or bags subject to repeated lifting, always verify that the SWL is rated appropriately for your load requirements.
4. What are the risks of consistently using oversized bags for lighter loads?
Oversized bags allow materials to shift during transport, increasing stress on seams and raising the risk of damage. They also reduce stacking efficiency, which can negatively impact storage capacity and logistics costs.
5. How should businesses approach sizing when working with multiple product types?
Each material should be calculated individually, as a one-size-fits-all approach can result in bags that are unsafe for denser loads or wasteful for lighter ones. A supplier can help identify a practical size range that works across your product portfolio without compromising safety
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