# How to Choose an FIBC Bulk Bag: Size, Tops, Bottoms, Loops and Liners

> A step-by-step guide to specifying a jumbo bag — calculating dimensions from bulk density, and choosing body type, filling top, discharge bottom, lifting loops, liners and coatings.

Published 2026-09-15 by Evergreen Packaging (Yantai Evergreen Packaging Co., Ltd.). Canonical: https://www.egpbags.com/blog/how-to-choose-fibc-bulk-bag/

**Key takeaways:** - Start from **bulk density and fill weight**, not from a catalogue size. ;; Volume (m³) = fill weight (t) ÷ bulk density (t/m³); then pick a base that fits your pallet. ;; **Spout top + spout bottom** for powders on filling lines; **open top + flat bottom** for firewood, aggregates and manual filling. ;; Add a **liner** for moisture-sensitive or fine powders, **baffles** to keep a square shape.

There is no universal "standard" jumbo bag. A good FIBC is designed around three things: the product inside it, the way it is filled and the way it is emptied. Specify those clearly and the right bag almost designs itself.

> **Skip the maths:** our free [bulk bag size calculator](/tools/bulk-bag-calculator/) does this calculation for you in seconds.

## Step 1: Know your product

Before anything else, write down:

- **Bulk density** in t/m³ (or kg/l). Flour is roughly 0.5–0.6, cement around 1.2–1.4, dry sand about 1.5–1.6, wood chips 0.2–0.3. Use your own measured value where possible.
- **Particle size and flow.** Fine powders sift through fabric and seams; coarse or sharp materials abrade.
- **Moisture sensitivity.** Hygroscopic products such as fertiliser, sugar and cement need a barrier.
- **Ignition risk.** Combustible dusts or flammable atmospheres need anti-static bag types.
- **Food or pharmaceutical contact,** which requires clean-room or food-grade production.

## Step 2: Set the fill weight and safety factor

The fill weight becomes the **safe working load (SWL)**. Most bags are rated 500–2,000 kg. Choose **5:1** for single-trip use or **6:1** for reusable bags; our [FIBC safety factor guide](/blog/fibc-safety-factor-5-1-vs-6-1/) explains the difference.

## Step 3: Calculate the dimensions

Required volume is simple arithmetic:

**Volume (m³) = fill weight (t) ÷ bulk density (t/m³)**

For 1 tonne of a product at 0.8 t/m³ you need about 1.25 m³. A filled FIBC bulges, so its usable volume is a little less than the geometric box. As a rule of thumb, choose a base that suits your pallet — 90 × 90 cm or 95 × 95 cm on a 100 × 120 cm pallet — and then set the height so that base × height gives roughly 10–15% more than the calculated volume.

| Product (example) | Bulk density | Fill weight | Typical size (cm) |
|---|---|---|---|
| Wood chips / firewood | 0.25–0.4 | 300–500 kg | 90 × 90 × 120 to 100 × 100 × 150 |
| Grain, feed pellets | 0.6–0.75 | 1,000 kg | 90 × 90 × 150 to 95 × 95 × 160 |
| Fertiliser | 0.9–1.1 | 1,000 kg | 90 × 90 × 120 |
| Cement, sand | 1.3–1.6 | 1,000–1,500 kg | 90 × 90 × 90 to 90 × 90 × 110 |

These are starting points; always confirm with a trial fill.

## Step 4: Choose the body construction

- **U-panel:** two pieces of fabric form a U, closed by two side panels. Strong, keeps its shape well and suits heavier loads.
- **Four-panel:** four side panels sewn together; good squareness.
- **Tubular (circular):** woven as a tube with no vertical seams, so fewer sifting points — preferred for fine powders.
- **Baffle (Q-bag):** internal fabric baffles across the corners keep the bag square when full, so it uses up to about 25–30% more container and warehouse space. See our [FIBC Virgin PP Breathable Tubular Jumbo Bulk Baffle](https://www.egpbags.com/products/fibc-bulk-bags/fibc-virgin-pp-breathable-tubular-jumbo-bulk-baffle-1000kg-woven/).
- **Vented:** mesh panels for firewood, potatoes and onions that must breathe.

## Step 5: Choose the top (filling)

- **Full open top** — fastest for manual or grab filling of aggregates and firewood.
- **Duffle / skirt top** — a fabric skirt that can be gathered and tied; protects contents and fits wide filling heads.
- **Filling spout** — a sleeve (often 35–45 cm diameter) that seals to the filling head of an automatic line; best for powders and dust control.

## Step 6: Choose the bottom (discharge)

- **Flat bottom** — the bag is cut open or tipped to empty; lowest cost, used for single-trip one-way loads.
- **Discharge spout** — a sleeve with a closure flap (often a "star" or petal closure) for controlled emptying into hoppers; essential for powders and granulates. Our [Large Capacity Jumbo Bag Integrated Discharge Outlet](https://www.egpbags.com/products/fibc-bulk-bags/large-capacity-jumbo-bag-integrated-discharge-outlet-for-bulk/) is an example.

## Step 7: Choose loops and extras

**Loops.** Cross-corner loops are sewn across each corner and are the most common choice for forklift handling. Side-seam loops are sewn into the vertical seams. Single- or two-loop designs suit crane hooks and high-volume mineral packing.

**Liners.** A polyethylene liner — loose, sewn-in or form-fit — protects moisture-sensitive or fine products and keeps food grades clean.

**Coatings and UV.** Coated fabric stops sifting and moisture; uncoated fabric breathes. Add UV stabilisation for any outdoor storage.

**Printing.** One or two sides, with your logo, product, SWL, safety factor and handling instructions.

## Our recommendation

If you are unsure, start with a **U-panel, 1,000 kg SWL, 5:1, 90 × 90 cm base, duffle top and discharge spout, cross-corner loops, coated fabric with PE liner** for powders — or an **open-top, flat-bottom, uncoated or vented** bag for coarse materials. Then fine-tune after a trial fill. Compare options in our [FIBC Bulk Bags](https://www.egpbags.com/products/fibc-bulk-bags/) range or send your product data and we will propose a drawing.

## Frequently asked questions

### What is the most common jumbo bag size?
For a 1,000 kg bag of medium-density product, 90 × 90 × 110–120 cm is the most common size because it fits standard pallets and containers well. The right height depends on your bulk density.

### Do I need a liner?
Use a liner if the product is fine enough to sift through seams, absorbs moisture or must meet food-hygiene requirements. Coarse, dry, non-food products usually do not need one.

### What is the difference between a U-panel and a tubular bag?
A U-panel bag has vertical seams and holds a square shape well; a tubular bag is woven as a seamless tube, which reduces sifting of fine powders.

### Can I get a drawing before ordering?
Yes. We provide a dimensioned drawing and specification sheet for approval, followed by a sample if required.

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Contact: doristeng2013@yt-evergreen.com · +86 186 6389 6305