FIBC Bag Calculator
Enter bag dimensions and your product's bulk density. The calculator returns volume, the weight your product will actually reach in that volume, and the fabric area the bag consumes. Works the same whether you call it super sack volume, jumbo bag capacity or FIBC sizing.
Calculator
Defaults show a standard 90 × 90 × 110 cm bag at 160 GSM with plastic resin at 0.6 t/m³. Switch to imperial for inches, lb/ft³ and pounds. Change any field — results update as you type.
Bulk Density Reference
Typical loose bulk density ranges for common FIBC cargo. These are industry reference figures — use your own measured value where you have one, since grade and moisture content both move the number.
| Material | t/m³ |
|---|---|
| Plastic resin pellets | 0.55 – 0.65 |
| Wheat, corn, grain | 0.70 – 0.80 |
| Cement, dry mortar | 1.20 – 1.50 |
| Sand, dry | 1.40 – 1.60 |
| Silica sand, aggregates | 1.50 – 1.70 |
| Metal ore concentrate | 2.00 – 3.00 |
How the Math Works
Volume (m³) = L × W × H, in metres
Load weight (kg) = Volume × Density × 1000
Fabric area (m²) = 2 × H × (L + W) + 2 × (L × W)
Fabric weight (kg) = Area × GSM ÷ 1000
Every figure above is plain geometry. Nothing here is a PackTonne quote, and nothing depends on which factory builds the bag.
Why Load Weight and SWL Rarely Match
A bulk bag's tonne rating is a load limit, not a capacity. Safe working load describes what the loops, fabric and seams are built to carry; volume describes how much space the bag encloses. The two only line up when your product happens to weigh about one tonne per cubic metre, and most products do not.
Plastic resin at 0.6 t/m³ fills a standard 90 × 90 × 110 cm bag to roughly 535 kg — barely half the rating. Cement at 1.4 t/m³ reaches the 1,000 kg limit before the bag is three-quarters full. Neither bag is wrong. They are the same bag meeting two different constraints: one runs out of volume, the other runs out of strength.
This is why bag height gets adjusted for dense cargo and widened for light cargo, and why quoting a bag by tonnage alone tells a supplier almost nothing. The related reading on 1-ton bags, SWL and safety factors covers how the rating itself is derived, and tare, net and gross weight covers which of these numbers customs and freight actually want.
What the Fabric Number Leaves Out
The fabric area returned here is clean geometric surface area: four sides, a top and a bottom. Real consumption at the factory is higher, and the gap comes from seam allowances, hem folds at the top and bottom, lifting loop webbing, and cutting waste that depends on how efficiently panels nest on the roll.
Construction changes it further. A circular woven body has no side seams and wastes less; a four-panel bag has four. Coating adds weight without adding area, and a liner is a separate material entirely. Use this number to compare two quotes for the same construction — that is what it is good for. See U-panel vs circular vs four-panel construction for how the body type changes the layout, and how to read a bulk bag spec sheet for the rest of the fields a real quote should carry.
Before You Send These Numbers to a Supplier
- 01Does your calculated load weight land above the bag's safe working load? If so, the bag is too big for your product — reduce the height, not the fabric weight.
- 02Does it land far below SWL? You are paying to ship air. A shorter bag carries the same tonnage in less container space.
- 03Is your bulk density a measured figure or an assumption? Tapped and loose density can differ by 15% or more, and the difference lands directly in your fill weight.
- 04Are you comparing quotes across suppliers? Fabric area times GSM is the closest thing to a like-for-like material comparison you can compute yourself.
- 05Does your product settle or bridge in transit? Baffle construction changes the effective volume, and this calculator models a plain bag.
Final Thoughts
The most useful output here is usually the mismatch. If your load weight lands at half the safe working load, you are shipping air and a shorter bag saves you freight; if it overshoots, no fabric upgrade fixes a bag that is simply too large for a dense product. Work out which of the two you have before you ask anyone for a price.
Calculation Questions
How do you calculate the volume of a bulk bag?
Multiply length by width by height in metres. A 90 × 90 × 110 cm bag gives 0.9 × 0.9 × 1.1 = 0.891 m³, or 891 litres — about 31.5 cubic feet and 1.17 cubic yards. This is the geometric volume when square-filled; a plain bag without baffles bulges under load and will not hold its rectangular shape in practice.
Why does my 1-ton bag not hold 1 ton of my product?
Because the tonne figure is a load rating, not a capacity. A bag rated for 1,000 kg safe working load filled with plastic resin at 0.6 t/m³ holds around 535 kg in 0.891 m³ of volume. The bag is not undersized — the product is simply lighter per cubic metre than the rating assumes.
How much fabric is in a bulk bag?
For a 90 × 90 × 110 cm bag, the four side panels plus top and bottom come to roughly 5.58 m² of fabric. At 160 GSM that is about 0.89 kg of woven polypropylene. Seams, hems, lifting loops and cutting waste are additional, and vary by construction and factory layout.
What does this calculator not include?
Seam allowances, hem folds, lifting loop webbing, liner material and cutting waste are all excluded. The fabric figure is a clean geometric surface area, useful for comparing quotes on a consistent basis. Actual consumption at the factory runs higher, and the gap depends on construction type and nesting efficiency.
Can I work in inches and pounds?
Yes. The imperial toggle takes dimensions in inches, bulk density in lb/ft³ and safe working load in pounds, and reports fabric weight in ounces per square yard rather than GSM. Switching back and forth does not change the bag you entered, only how it is displayed.
Which bulk density figure should I use?
Use the loose or poured bulk density of your product, not the tapped figure, unless your filling process actively densifies the load. The two can differ by 15% or more. If you do not have a measured value, your material supplier or the product safety data sheet is the right source.
Does bag construction change the volume calculation?
Yes, in practice. A U-panel or circular bag bulges under load and loses usable height, while a baffle bag holds closer to its nominal rectangular shape. This calculator returns the geometric volume, which sits closest to real capacity for baffle construction and slightly overstates it for plain bags.
Can I use fabric area to estimate what a bag should cost?
Fabric area times GSM gives you material weight, which is the largest single input into a bag price but not the whole picture. Loops, thread, liner, printing, certification and testing all sit on top. Use it to compare two quotes for the same specification, not to predict an absolute price.
Send Us the Numbers You Just Calculated
Dimensions, bulk density and target load weight are enough for us to confirm a construction and fabric weight — or tell you the bag size should change before anything else does.
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