Export Packaging: Bags, FIBC & Liquid Containers
Bulk density decides your packaging before anything else does. Find your material, see whether the shipment runs out of weight or of space first, then pick the sack, big bag or liquid container that suits it — and generate a specification your supplier can quote against. Everything runs in your browser.
Every figure in the table below is a typical range for a typical grade. Your material will differ, sometimes by a third, and the difference lands straight on your freight bill. Measuring it takes one weighing.
- Take a clean container of known volume — a 10-litre bucket is ideal — and weigh it empty.
- Fill it from the same height and in the same way your bagging line does, without shaking or pressing down.
- Strike the top level and weigh it full.
- Bulk density in t/m³ = net kilograms ÷ litres. Ten litres holding 12 kg gives 1.20 t/m³.
Do it on material at the moisture it will actually ship at. A powder that has picked up damp weighs more per cubic metre without occupying any less space, so a wet cargo weighs out sooner than the dry figure predicts.
An estimate. Stowage efficiency is an assumption, not a measurement — the real figure depends on pallet pattern, bag shape and how the container is loaded. Work the actual pattern out in the 3D Pallet Calculator and the 3D Container Stuffing Calculator.
A sack's length and width come from the bag your supplier makes; its thickness comes from your material. The same 60 × 50 cm sack is about 11 cm thick filled with cement and three times that filled with metakaolin, so thickness is calculated here rather than quoted from a table.
Liquid containers are the one family where the dimensions really are standard, because the container is rigid and the liquid takes its shape. These are the common formats; confirm against your supplier's drawing before you plan a pallet pattern.
| Container | Nominal volume | Typical outside dimensions | Notes |
|---|
Enter the filled dimensions a supplier or freight quote has given you. The implied density is worked back and compared with your material's range, which catches the commonest error: a sack size copied from a different product.
| Material | Typical t/m³ | m³ per tonne | Notes |
|---|
Planning ranges for typical grades, not specifications. Moisture, particle size, grade and how the material is filled all move these figures, and settling in transit moves them again. Measure your own material before you commit to a packing plan or quote a freight rate.
The commonest reason wrong packaging arrives is a specification that left the decision to the supplier. Fill in what you know, leave the rest as blanks for them to propose against, and send it with your enquiry.
The specification follows whichever packaging family is selected above, and carries the material, density and unit weight from the calculator.
Why bulk density comes before packaging
A container has two ceilings: the weight it may legally carry and the space inside it. Which one you hit first is decided almost entirely by how much a cubic metre of your material weighs, and that single number drives the rest of the packing decision — sack size, pallet pattern, whether big bags make sense, and what your freight actually costs per tonne delivered.
The extremes make it obvious. Expanded perlite at around a tenth of a tonne per cubic metre fills a forty-foot high cube at roughly seven or eight tonnes: you are paying ocean freight largely to move air, and nothing you do to the packaging changes that. Barite powder at over two tonnes per cubic metre reaches the payload limit with the container barely a third full: here the whole problem is weight, and a bigger sack only makes the pallet harder to handle. Portland cement sits near the balance point, which is why cement is shipped in so many different formats depending on the trade.
Two consequences follow that catch exporters out. First, quoting freight per tonne for a light material understates the cost badly, because the container that carries it holds far fewer tonnes than the carrier's average. Second, a material that weighs out leaves usable space you have already paid for, which is sometimes worth filling with a denser co-loaded product if your customer takes both.
Sack sizes: the range is wider than most exporters assume
Cement, gypsum, plaster and similar construction powders ship in anything from ten kilograms to fifty, and the choice is usually about the buyer's market rather than about the product. Fifty kilograms remains the classic bulk-trade size and is the cheapest per tonne in packaging cost, but it is above what many markets now permit for routine manual handling, and several countries have pushed the standard down to twenty-five. Retail and DIY channels want ten, fifteen or twenty kilogram packs that one person can carry from a shelf to a car, and they will pay for the printing that goes with them. Twenty-five kilograms has become the common middle ground for export because it handles safely, palletises cleanly and still keeps packaging cost per tonne reasonable.
Smaller sacks cost more per tonne in three separate ways: more bags for the same tonnage, more filling-line time, and worse pallet utilisation because the void fraction between small bags is higher. Against that, they open retail channels and reduce handling claims. Work the comparison in money per tonne delivered rather than in price per bag, and include the pallet pattern, because a size that palletises badly can lose more in freight than it saves in packaging.
Why a sack's thickness cannot be looked up
Length and width belong to the bag: the supplier makes it to a flat size, and a 50 kg sack is commonly around 60 by 50 centimetres. Thickness belongs to the material. The sack holds whatever volume the net weight occupies, so the same bag comes out about 11 centimetres thick filled with cement and over 30 filled with metakaolin, which is roughly a third as dense. Any table that prints a single thickness for “a 50 kg sack” is really printing it for one material and getting every other one wrong.
There is a second effect worth knowing. Powder inside a filled sack is denser than the same powder poured loose, typically by twenty to thirty per cent, because filling and then stacking consolidates it. Cement at 1.23 tonnes per cubic metre loose behaves like roughly 1.54 in the sack, which turns 50 kg into about 32 litres and, across a 60 by 50 sack, into just under 11 centimetres. That is why a measured sack looks denser than the published bulk density, and why the calculator carries a compaction factor you can adjust rather than assuming the two are the same.
The same arithmetic governs big bags, and there it changes what you can ship. A one-tonne bag on a 90 by 90 centimetre base needs about a metre of filled height for cement, which fits comfortably under a container door. The same bag of metakaolin would need over three metres, which fits nothing. Light materials are shipped in big bags at half a tonne or less, not because the fabric cannot take a tonne, but because a tonne will not fit inside a bag that can still go through the door.
Choosing between the four families
Cement and lime are filled with entrained air that has to escape as the sack settles, and multiwall kraft paper lets it out through the porous plies while holding the powder. Paper also prints beautifully, which matters for retail. Its weakness is water: a paper sack that gets wet on a quay is finished, and on humid trades a polyethylene ply or a free film liner is not optional.
Woven polypropylene tolerates rough handling, repeated stacking and humidity far better than paper, which is why rice, sugar, fertiliser and most minerals move in it. Laminated fabric adds a moisture barrier and a printable surface; an inner polyethylene liner adds a proper one. The trade-off is breathability: a fully sealed PP bag on a hot trade can trap condensation against the product.
One big bag replaces twenty or forty sacks, which cuts filling time, labour and handling claims dramatically. It only works if the receiver has a forklift or crane with the reach to lift a tonne, and somewhere to discharge it. Where the buyer breaks bulk by hand at the far end, big bags shift your cost onto their labour and they will notice.
Below a pallet or two, jerrycans and drums. Up to a container load of separate lots, intermediate bulk containers. For a single full-container parcel of a non-hazardous liquid, a flexitank carries far more than drums or IBCs in the same box. Above that, or for regulated products, an ISO tank container. Whether the product is dangerous goods usually removes flexitanks from the list immediately.
Where liquid shipments go wrong
The mistake is treating a flexitank's nominal capacity as something you can fill. A twenty-four thousand litre flexitank of sunflower oil weighs about twenty-two tonnes, which fits a twenty-foot payload. The same tank of molasses would weigh over thirty-four tonnes, which does not fit anything. For any liquid heavier than water, the tank size you can actually use is set by payload divided by specific gravity, not by the tank's rating, and the calculator above applies exactly that.
The second issue is one-way economics. Flexitanks are single-use and disposed of at destination, which is simple but means your buyer handles the disposal. Intermediate bulk containers and drums may have to come back or be bought outright, and an ISO tank is leased with demurrage of its own running from the day it arrives. Establish who owns and who returns the equipment before you compare prices, because an apparently cheaper option that requires repositioning is rarely cheaper.
- Once you know the sack or big bag, work the actual pattern in the 3D Pallet Calculator and the 3D Container Stuffing Calculator.
- Packaging weight counts towards the declared weight: the SOLAS VGM Calculator.
- Compare formats in money per tonne delivered with the Landed Cost Estimator.
- Regulated liquids and powders change the options entirely: the Dangerous Goods (IMDG) Reference.
- Material-specific buyer's guides for several of the minerals in the table: anhydrite, metakaolin, perlite and calcined shale.
Frequently asked questions
It is the weight of a cubic metre of material as it sits loose in a bag or a hold, including the air between the particles. It matters because it decides whether a container fills up by weight or by volume first. A light material means you pay freight for space you cannot fill with tonnes; a heavy one means you reach the weight limit with the container part empty.
Anywhere from ten to fifty kilograms. Fifty is the traditional bulk-trade size and the cheapest per tonne; twenty-five has become the common export size because it handles safely and palletises well; ten to twenty kilogram packs serve retail and DIY channels. Several markets now cap manual handling below fifty, so check the destination before assuming.
A 50 kg cement sack is commonly about 60 by 50 centimetres flat, and roughly 10 to 11 centimetres thick once filled. The thickness is not a fixed property of the bag: it is the filled volume divided by the flat area, so it follows the density of what is inside. The same sack filled with a lighter powder is far thicker, and the calculator on this page works it out for whatever material you select.
Big bags are specified by safe working load rather than by volume, most commonly between five hundred and two thousand kilograms, with one tonne the usual export size. The volume you need follows from your bulk density: a tonne of a material at one tonne per cubic metre needs a cubic metre of bag, while a tonne of something at half that density needs two.
They are electrostatic classifications. Type A is plain fabric with no static protection and is for non-flammable products in non-flammable surroundings. Type B is built so it cannot produce the most dangerous kind of discharge but still must not be used where flammable vapour is present. Type C is conductive and must be earthed during filling and discharge, and is unsafe if the earth is not connected. Type D dissipates static without earthing. Choosing between them depends on the product and the atmosphere at both ends, so confirm it with your safety advisor rather than with your bag supplier alone.
No. The usable volume is the container's payload divided by the liquid's specific gravity. Water-like liquids get close to the tank's rating; anything appreciably heavier, such as molasses or a juice concentrate, hits the payload limit well before the tank is full. Dangerous goods are generally excluded from flexitanks altogether.
They are typical ranges for typical grades, meant as a starting point. Your own material can sit outside them, because moisture, particle size, grade and filling method all move the figure. The page shows you how to measure yours in a few minutes, and the calculator accepts your measured value in place of the table's.
Reference information for planning purposes only. Packaging specifications, safe working loads, electrostatic classification and dangerous goods requirements must be confirmed with your packaging supplier, your carrier and, where relevant, a qualified safety advisor.