Gross Weight vs Net Weight vs Volumetric Weight Explained

Gross weight vs net weight vs volumetric weight is where export quotes quietly go wrong: you weigh the product, quote the freight, and the carrier bills you for air. The carton weighs 20 kg. The invoice says 36 kg. Nobody made a mistake — you just quoted the wrong number.

Four numbers describe the same carton, each belonging to a different party. Your buyer wants one. Your carrier bills a second. Customs taxes a third. Put the wrong one on your spec sheet and you collect all three classic outcomes: a freight surprise, a buyer dispute, and a quote you have to eat.

Gross Weight vs Net Weight vs Volumetric Weight: What Each One Means

• Net weight is the goods themselves, with no packaging at all — UK customs defines it as "the weight of the goods themselves without any packaging."
• Tare weight is the empty packaging — carton, pallet, crate, or shipping container — with no cargo inside.
• Gross weight is net weight plus tare weight. (Its scope changes depending on who's asking — this is the one that burns people.)
• Volumetric weight — also called dimensional weight or DIM weight — is not a weight at all. It's the space your cargo occupies, converted into kilograms so the carrier can price it.
• Chargeable weight is what the carrier bills. Maersk defines it as "the quantified weight used to calculate the freight rate" — the figure on your invoice.

The arithmetic is fixed: Gross weight = Net weight + Tare weight — so net = gross − tare, and tare = gross − net.

Here's the sentence to keep: your carrier does not bill what your product weighs — it bills whichever costs it more, the weight or the space.

The Divisor That Decides Your Freight Bill

Volumetric weight comes from a tape measure, not a scale. The standard metric formula, per Maersk:

Volumetric weight (kg) = (Length × Width × Height in cm) ÷ 6000

The 6,000 divisor is an industry standard set by the International Air Transport Association (IATA). In imperial units the same calculation uses a divisor of 366: volumetric weight (lbs) = (L × W × H in inches) ÷ 366.

Then the rule that matters: chargeable weight is based on the higher of two values — actual weight (gross weight) or volumetric weight. Not the average. Not the one you prefer. The higher one.

Maersk's worked example, on a 100 × 60 × 30 cm carton:

(100 × 60 × 30) ÷ 6000 = 30 kg volumetric weight

• If that carton's actual gross weight is 50 kg → volumetric (30) is lower → you're billed on 50 kg.
• If that carton's actual gross weight is 20 kg → volumetric (30) is higher → you're billed on 30 kg. You just paid for 10 kg of air.

Why 6000 isn't the only divisor

Not every carrier uses the IATA number. Maersk states that "some carriers use a divisor of 5,000 instead of 6,000 to calculate volumetric weight, which results in bulkier shipments being charged at a higher rate," and that express carriers run their own formulas, varying by origin and destination. Confirm the divisor before you book.

The same carton (180,000 cm³) through both divisors:

Same box, same goods. Six kilos of difference, decided by a number in a tariff document you never read.

The break-even density nobody tells you

Divide 1 m³ (1,000,000 cm³) by the divisor to get the density at which volumetric weight stops mattering:

Now look at what you ship. Flat-pack furniture, light fixtures, insulation panels, plastic profiles — anything with void space sits well under 167 kg/m³. If you export bulky goods, volumetric weight isn't an edge case; it's your default billing basis.

Sea freight plays the same game with different numbers

Ocean LCL doesn't use the 6000 divisor — it bills on W/M (weight or measurement). For LCL cargo, 1 CBM is taken as equal to 1,000 kg (1 metric ton); the carrier calculates both ways and bills the higher.

That 100 × 60 × 30 cm carton is 0.18 CBM. At 20 kg it's 0.02 metric tons — volume wins by nine times, so you're billed on 0.18 revenue tons. Since manufactured goods sit far below 1,000 kg/m³, measurement wins for nearly anything that isn't steel or stone.

When Each Weight Matters

Note the split: the number that sets your tax (net) and the one that sets your freight (chargeable) are different figures. A spec sheet with only one is incomplete.

Common Confusion Points

"Gross weight" means two different things

This is the expensive one, and almost nobody flags it.

In carrier language, Maersk defines gross weight as your products plus packaging, pallets, and the container — excluding only the truck. Their example: 8,400 tins of coffee at 200 g each, loaded into a 20-foot container, comes to 1,680 kg (coffee) + 300 kg (packaging and pallets) + 2,280 kg (container) = 4,260 kg gross weight. (A standard Maersk 20-foot container tares at 2,280 kg / 5,030 lb; the 40-foot at roughly 3,700 kg.)

In customs language, it's not the same figure. UK customs defines gross mass as "the total weight of the goods and packaging but excluding containers and any other transport equipment." Run that same shipment through this definition and the declarable gross mass is 1,980 kg — the 2,280 kg container is explicitly out of scope.

Same shipment. Two legitimate "gross weights," 2,280 kg apart. When your forwarder and your customs broker quote different gross figures, this is usually why.

A related trap: UK guidance says pallet weight appearing in the transport documents must also be included in gross mass — unless the pallet is a separate declaration item or the import licence is based on gross weight.

Net weight is what gets taxed, so precision isn't optional

Import duties and taxes are usually based on net weight — not the packaging, not the container. UK customs asks for net mass in kilograms and accepts up to 6 decimal places. "About 15 kg" is not a net weight; it's a guess a customs officer can price.

Volumetric weight is measured, never weighed

No scale produces volumetric weight. It comes entirely from your outer carton dimensions, which means a sloppy carton measurement is a sloppy freight quote, every time. Measure the carton packed and sealed, at its widest real point, bulges included. If your cartons are the weak link, start with master carton dimensions before touching your weight table.

Put the Numbers Where the Buyer Actually Looks

Perfect weight math is worth nothing if the buyer never opens the PDF. Most weight disputes don't start with a bad number — they start with a correct number nobody saw.

The fix isn't a longer document. It's locking the measured carton dimensions and the weight block onto the product image itself, where buyers look before they ask. Tools like snap-to-edge dimension annotators let you pin the actual measured carton size to the photo, carry cm and inch together for the buyer's market, and export at each platform's spec size in one click.

Accuracy matters here more than anywhere else in your listing. Deterministic geometry pins the size you genuinely measured; an AI-generated image will happily invent a dimension that looks plausible and is wrong. A wrong carton dimension isn't cosmetic — it's a wrong volumetric weight, so a wrong chargeable weight, so a wrong quote you're contractually holding. The same mechanics apply to how to label weight capacity on product images.

The Weight Block to Put on Every Export Spec Sheet

Copy this into your spec sheet and fill every row. A blank row is an email from your buyer.

Publishing all of it kills the "what's the shipping weight?" thread and makes your quote defensible when the invoice lands. The same logic drives a strong export quotation — the weight block is what buyers verify first.

Pre-Send Checklist

• Net weight measured with packaging removed, not back-calculated
• Gross weight stated, specifying whether it includes the pallet
• You know which "gross" your customs broker needs (container excluded)
• Master carton measured packed and sealed, at its widest point
• Divisor confirmed in writing with the forwarder — not assumed to be 6000
• Chargeable weight = greater of gross vs volumetric, and freight quoted on it
• CBM stated per carton and per pallet
• Units labeled (kg/lb, cm/in) on every figure
• Weights and dimensions on the product image, not only in the PDF

Wrong weights cost more than freight — they trigger disputes, refused deliveries, and returns, each with its own margin math. The return cost calculator puts a number on what one of those takes out of an order.

FAQ

What is the difference between gross weight and net weight?

Net weight is the goods alone; gross weight is the goods plus packaging. Gross weight = net weight + tare weight, where tare is the empty carton, pallet, or container. The catch is scope: carriers count the shipping container inside gross weight, while UK customs defines gross mass as goods and packaging but excluding containers. Always ask which definition a given number was built on.

How do I calculate chargeable weight for air freight?

Calculate both weights and take the higher one. Volumetric weight (kg) = (L × W × H in cm) ÷ 6000, using IATA's standard divisor; compare that to your actual gross weight; the larger figure is the chargeable weight. For a 100 × 60 × 30 cm carton, volumetric weight is 30 kg — so a 50 kg carton bills at 50 kg, but a 20 kg carton bills at 30 kg. Confirm your carrier's divisor first, since some use 5,000 and produce a higher bill on the identical box.

Is volumetric weight the same as dimensional weight?

Yes — volumetric weight, dimensional weight, DIM weight, and volume weight all name the same thing: your shipment's space converted into kilograms so it can be priced. The terminology shifts by region and carrier; the mechanism is identical. What varies between carriers isn't the name, it's the divisor.

Why is my freight bill higher than the actual weight of my shipment?

Because your cargo is lighter than its break-even density, so you were billed on volumetric weight. At IATA's 6,000 divisor, anything under roughly 167 kg/m³ bills on space rather than mass; at 5,000 that threshold rises to 200 kg/m³; on ocean LCL, where 1 CBM is treated as 1,000 kg, almost all manufactured goods bill on volume. Bulky, lightweight products get charged for the air inside the carton — the system working as designed, not an error.

Which weight should I put on my export spec sheet?

All four, labeled: net weight, gross weight (packed), carton dimensions with CBM, and volumetric weight at your carrier's divisor. Buyers recalculating landed cost need net and gross; anyone estimating freight needs dimensions and volumetric weight; customs needs net mass. Publishing one and leaving the rest to email is how gross weight vs net weight vs volumetric weight becomes a dispute instead of an order.

Sources & References

• Maersk — Air cargo chargeable weight calculation explained (10 Mar 2025): the IATA 6000 divisor, the imperial 366 divisor, the higher-of-two rule, carrier variation to 5,000.
• Maersk — Shipping weight guide: Tare, net, and gross weight explained (updated 25 Jun 2025): tare/net/gross formulas, container tare weights, duties on net weight, IMO Verified Gross Mass.
• GOV.UK — Import Declaration Completion Guide, Group 6: Goods Identification: customs definitions of net mass and gross mass, the container exclusion, the pallet rule.
• Marine Insight — What Is CBM Rate In Shipping?: the ocean LCL W/M convention, 1 CBM treated as 1,000 kg, billed on the higher.