Four crates go on the scale and read 420 lb. The air waybill comes back billed at 680 lb. Nothing was added to the shipment and nobody made a mistake: the carrier charged on chargeable weight, and on this shipment chargeable weight was 260 lb heavier than what the scale said.
That gap is the single most common surprise on a first air freight invoice, and it is also why the difference between gross weight and net weight matters in practice rather than as a definition. Net weight, gross weight and chargeable weight are three different numbers on the same shipment. One of them sets your rate. The other two decide whether your paperwork clears and whether your load is legal on the road.
This guide defines all three, shows the arithmetic on a real shipment, and ends with the six fields our team needs in order to price your freight instead of estimating it.
The three weights on one shipment
Take the same four crates of packaged auto parts and read them three ways.
| Weight | What it counts | On these four crates | What it decides |
|---|---|---|---|
| Net weight | The goods only | 316 lb | Customs value, duty, inventory, product labelling |
| Gross weight (actual weight) | Goods plus packaging, pallet, dunnage and strapping | 420 lb | Axle limits, handling equipment, aircraft loading, safety |
| Chargeable weight | The greater of gross weight and volumetric weight | 680 lb | The rate you pay |
Read the table one more time and the practical rule falls out. Net weight is a customs and compliance number. Gross weight is a physics and safety number. Chargeable weight is a commercial number, and it is the only one of the three that your carrier multiplies by a rate.
What is net weight?
Net weight is the weight of the goods themselves, with nothing else included. No carton, no pallet, no shrink wrap, no corner board, no ice pack. If you sell 200 bearings and each bearing weighs 1.58 lb, the net weight of that shipment is 316 lb whether they travel loose in one crate or split across four.
How to calculate net weight
There are two ways, and you should agree with your supplier on which one is being used before the goods are packed.
- Bottom up. Unit weight multiplied by unit count. This is the accurate method and the one your commercial invoice should reflect.
- Top down. Gross weight minus tare weight, where tare weight is everything that is not the product. This works when the goods are already packed and cannot be opened.
Net weight is what customs authorities reconcile against your declared value, so a net weight that contradicts the commercial invoice is one of the fastest ways to have a shipment pulled for inspection. It is also the number that belongs in the product description on your packing list, not in the weight field of the transport document.
What is gross weight?
Gross weight is everything the carrier physically picks up: the goods, the primary packaging, the outer carton, the pallet or skid, the dunnage inside the box, the stretch wrap, the banding and any ice or gel packs that travel with the load. On an air waybill and on most domestic rate quotes this same number is called actual weight.
How to calculate gross weight
Gross weight equals net weight plus tare weight. On our four crates:
- Net weight of the parts: 316 lb
- Four wooden crates at 20 lb each: 80 lb
- Internal foam, wrap and banding: 24 lb
- Gross weight: 420 lb
The mistake worth naming here is estimating tare rather than weighing it. Packaging on industrial freight routinely runs 15 to 30 percent of the total, and on light high value goods it can exceed the product. A shipper who quotes net weight to a carrier and gross weight to nobody will be re-weighed at the terminal and re-rated afterwards.
Gross weight, net weight and tare weight in one line
Gross weight = net weight + tare weight. Rearranged, tare weight is what you are paying to ship that is not your product, which makes it a packaging design question as much as a logistics one. On the road the same identity has a legal edge: state axle limits are written against gross vehicle weight, so the tare of the trailer and the tare of your packaging both eat into the payload you are allowed to carry. Our state by state guide to legal axle weight limits covers where those ceilings sit, and how many pallets fit in a truck covers the floor space side of the same trade off.
What is chargeable weight, and why it is usually the biggest number
An aircraft runs out of room before it runs out of lift. A pallet of insulation and a pallet of steel fittings occupy the same position in the hold, and if both were billed by the scale the insulation would travel almost for free. Carriers solve this by converting your volume into a weight, then charging on whichever number is larger.
Chargeable weight is the greater of gross weight and volumetric weight. That is the whole rule. Everything else is arithmetic on the volumetric side.
The air freight formula
Volumetric weight, also called dimensional weight or DIM weight, is calculated per piece:
Length × width × height (inches) ÷ 166 = volumetric weight in pounds
In metric the same rule is length × width × height in centimetres divided by 6,000, which gives kilograms. The two divisors are the same standard expressed in different units, and 166 is the IATA figure most international air carriers publish.
Three details decide whether your number matches the carrier’s:
- Measure the piece as it ships, not as it was built. If the goods sit on a 5.5 in pallet, the pallet height counts. If a bracket overhangs the skid by two inches, the carrier measures to the widest point of the overhang.
- Measure after packing. Crating, corner protection and shrink wrap add inches on every axis, and the cubic figure is a product of three of them.
- Round the way the carrier rounds. Most tariffs round each dimension up to the next whole inch or half centimetre before the multiplication, which is why a 20.2 in height is billed as 21 in.
Worked example: 420 lb that ships as 680 lb
Back to the four crates. Each one measures 42 × 32 × 21 inches after packing and weighs 105 lb on the scale.
- Volume per crate: 42 × 32 × 21 = 28,224 cubic inches
- Total volume: 28,224 × 4 = 112,896 cubic inches
- Volumetric weight: 112,896 ÷ 166 = 680 lb
- Gross weight on the scale: 420 lb
- Chargeable weight: 680 lb, because volumetric is the larger of the two
At a rate of 2.40 USD per pound that is 1,632 USD instead of the 1,008 USD the scale suggested. The 624 USD difference was created in the packing area, not in the pricing department, and it is recoverable: take four inches off the height of each crate and the volumetric weight drops to 551 lb, which is still above gross but 129 lb cheaper.
The crossover point is worth knowing by heart. At the 166 divisor, freight denser than roughly 10.4 lb per cubic foot is billed on its scale weight, and anything lighter is billed on its volume. Insulation, packaging materials, plastic housings, apparel, empty enclosures and most retail returns sit on the light side of that line almost every time.
Why your quote might say 812 lb instead
The divisor is not a law of nature, it is a term in a tariff, and the same crates priced under a different divisor produce a different bill:
| Divisor | Where you meet it | Chargeable weight on the same 112,896 cubic inches |
|---|---|---|
| 194 | Some consolidated and deferred air services | 582 lb |
| 166 | IATA standard, most international airport to airport air freight | 680 lb |
| 139 | Domestic parcel and express air tariffs | 812 lb |
Same freight, same scale reading, a 230 lb spread in what you are billed on. Before you compare two air quotes, confirm they were built on the same divisor. Comparing a 139 quote against a 194 quote tells you nothing about which carrier is cheaper.
Chargeable weight on the ground works differently
Domestic LTL does not use a divisor. It uses density to assign a freight class, and the class is what drives the rate. The arithmetic starts the same way and then turns:
- Cube the pallet in cubic feet: length × width × height in inches divided by 1,728.
- Divide gross weight by that cubic figure to get pounds per cubic foot.
- Read the density into a class band, then confirm the commodity against its NMFC item, because some commodities are classed by what they are rather than by how dense they are.
Our four crates cube out at 65.3 cubic feet and weigh 420 lb, which is 6.4 lb per cubic foot and puts them in a high class band. Use the NMFC code lookup to find the item number for your commodity, and read NMFC freight classes and subclasses if the density bands themselves are new to you.
The practical consequence is that the same shipment can be cheap by air and expensive by LTL, or the reverse, and you cannot tell which without running both. That is what a freight calculator is for at the estimating stage, and what understanding freight rates covers on the accessorial and fuel side once the base number exists.
Give us six fields and we will price it
Every worked example on this page is arithmetic on assumptions. Your shipment has real dimensions, a real ready date and a real commodity, and the only way to know what it costs is to run it. These are the six fields our air desk needs:
- Origin and destination. Airport codes if you know them, ZIP codes if you do not.
- Piece count. How many crates, skids or cartons move as one shipment.
- Dimensions of each piece in inches, measured after packing, to the widest point including any overhang.
- Actual weight of each piece in pounds, from a scale rather than an estimate.
- Ready date and required delivery date. The gap between them is what decides whether this is standard air, express or a charter.
- Commodity and handling notes. What it is, whether it stacks, and whether it is hazmat, temperature controlled or oversized.
Send those six and you get a chargeable weight and a rate, with the divisor we used stated on the quote so you can check the arithmetic yourself. Start on our air freight shipping services page and use the contact form there.
If you are still deciding whether air is the right mode at all, the benefits of air freight shipping sets out where it pays for itself, and when freight needs an air charter covers the cases where scheduled service will not hold the date.
Where each weight has to appear on the paperwork
Getting the three numbers right is only half the job. Putting each one in the correct field is the other half, and a weight in the wrong box causes the same delays as a weight that is wrong.
| Document | Which weight goes in it |
|---|---|
| Air waybill, gross weight field | Gross weight, the scale reading including all packaging |
| Air waybill, chargeable weight field | Chargeable weight, the greater of gross and volumetric |
| Bill of lading | Gross weight per handling unit, plus class or NMFC item on LTL |
| Commercial invoice and customs entry | Net weight, reconciled against declared value |
| Packing list | Both net and gross, per carton, so the two can be checked against each other |
Our air waybill guide walks through the AWB field by field, and the bill of lading guide does the same for surface moves.
Five mistakes that change the invoice
- Quoting net weight to the carrier. The carrier rates on gross and chargeable. A quote built on net weight is low by the entire tare and will be re-rated at the terminal.
- Measuring before packing. Crating and wrap add inches on all three axes, and volume is the product of three numbers. Add one inch to each dimension of a 42 by 32 by 21 crate and its volumetric weight rises by 18 lb; across four crates that is 72 lb of freight nobody weighed.
- Ignoring the pallet. Pallet height counts toward the cube and pallet weight counts toward gross. A 48 by 40 skid adds around 5.5 inches and 35 to 50 lb before anything is loaded onto it.
- Assuming your divisor. A quote at 139 and a quote at 194 are not comparable. Ask which divisor the tariff uses and confirm it appears on the rate confirmation.
- Averaging across pieces. Volumetric weight is calculated per piece and then summed. Averaging dimensions across a mixed shipment understates the total whenever the pieces differ in shape.
How to keep the numbers accurate
- Weigh the finished unit on a calibrated floor or pallet scale rather than adding up component weights from a spec sheet.
- Record dimensions with a tape at the widest and tallest points of the packed unit, including overhang, and round each up to the next whole inch.
- Keep a standing tare figure for each crate or skid type you use, and recheck it whenever packaging changes.
- Write net, gross and chargeable weight on the packing list for every shipment, even domestic ones, so any dispute can be settled from your own records.
- Photograph the packed unit next to the scale display. It costs nothing and it is the only evidence that survives a re-weigh dispute two weeks later.
Frequently asked questions
What is the difference between chargeable weight and gross weight?
Gross weight is what the shipment weighs on a scale, including packaging and pallets. Chargeable weight is the number the carrier bills on, and it is the greater of gross weight and volumetric weight. When freight is dense the two are the same. When freight is light and bulky, chargeable weight is higher, sometimes by several hundred pounds.
Is chargeable weight ever lower than gross weight?
No. Chargeable weight is defined as the greater of the two, so it is either equal to gross weight or higher than it. If a quote shows a chargeable weight below the scale reading, the dimensions or the piece count on that quote are wrong.
What is the difference between gross weight and net weight?
Net weight is the goods alone. Gross weight is the goods plus everything used to pack and move them: cartons, crates, pallets, dunnage and wrap. Gross weight minus net weight is tare weight. Customs works from net weight, carriers work from gross weight.
Which weight decides my air freight rate?
Chargeable weight. Multiply your packed dimensions in inches, divide by the divisor in your carrier’s tariff, and compare the result against the scale reading. The larger figure is multiplied by the rate per pound.
Does the 166 divisor apply to my shipment?
It applies to most international airport to airport air freight, because 166 cubic inches per pound is the IATA standard, equivalent to 6,000 cubic centimetres per kilogram. Domestic parcel and express services commonly use 139, and some consolidated or deferred services use 194. Ask before you compare quotes.
Conclusion
Net weight, gross weight and chargeable weight are not competing definitions of the same thing. They are three separate numbers with three separate jobs, and confusing them costs money in the one direction that is easy to miss: the invoice arrives correct and you have no way to explain it.
Weigh the packed unit, measure it after packing, run the volumetric calculation at your carrier’s divisor, and bill yourself on the larger of the two before anyone else does. When you want the real number rather than an estimate, send us the six fields above through our air freight shipping services page and our team will price the shipment and show the arithmetic.
