Short answer: Couriers charge for the space a box takes up, not only for what it weighs. They work out a dimensional weight from the box's length, width and height, compare it with the actual weight, and bill the higher of the two. Each courier uses its own divisor, so the same box can have a different dimensional weight with each one.
What dimensional weight is
A plane or truck fills up by space as well as by weight. A large box of pillows weighs little but takes the room of a much heavier parcel, so couriers price it as if it were heavier.
That's why every shipment has two weights:
- Actual weight: what the package weighs on a scale.
- Dimensional weight: a weight worked out from the box's size.
The courier bills whichever is higher. We call that the billable weight.
How it's calculated
Multiply the box's three sides in inches, then divide by the courier's divisor:
Length × Width × Height ÷ divisor = dimensional weight in pounds
We measure every package when it arrives at our warehouse, so you don't need to measure anything yourself. The billable weight is then rounded up to the next whole pound for every courier except APC.
Divisors by courier
The divisor is what makes the difference between couriers. A higher divisor gives a lower dimensional weight, which is better for you.
| Courier | Divisor | What it means for a bulky box |
|---|---|---|
| UPS | 200 | Lowest dimensional weight of our couriers |
| DHL | 166 | In the middle |
| FedEx | 166 | In the middle |
| Aramex | 139 | Highest dimensional weight — bulky boxes cost more |
These divisors come from our agreements with each courier, so they can differ from the numbers on a courier's own website. For our other couriers, compare the price shown at checkout.
A worked example
Take a box that measures 20 × 16 × 12 inches and weighs 6 lb on the scale. Its volume is 3,840 cubic inches.
| Courier | Dimensional weight | Billable weight |
|---|---|---|
| UPS (÷ 200) | 19.2 lb | 20 lb |
| DHL, FedEx (÷ 166) | 23.1 lb | 24 lb |
| Aramex (÷ 139) | 27.6 lb | 28 lb |
The box weighs 6 lb, but with every courier it's billed on its size. The same box costs 20 lb with UPS and 28 lb with Aramex, so comparing couriers matters most for light, bulky shipments.
How to lower your dimensional weight
- Ask us to repack. Stores often ship small items in large boxes full of filler. A better-fitting box can cut the dimensional weight sharply. See "Repacking and removing items".
- Be careful when combining bulky items. Consolidating usually saves money, but one large item can push the whole box into a higher dimensional weight. See "Consolidating packages: how to request it, how long it takes and what it costs".
- Compare couriers at checkout. For a light, bulky box, the courier with the highest divisor often gives the lowest price. See "Carriers and shipping services we use".
- Check before you buy. If a product page lists the box size, you can estimate the dimensional weight before you order. See "Estimating your shipping cost and delivery time".
Common questions
My item is light. Why am I paying for so much weight? Because the box is big. When the dimensional weight is higher than the actual weight, the courier bills the dimensional weight. Asking us to repack into a smaller box is usually the quickest fix.
Why does the same package have a different weight with each courier? Each courier divides the box's volume by a different number. A higher divisor gives a lower dimensional weight, so the billable weight can change from one courier to the next.
Do I need to measure my package? No. We measure and weigh every package when it arrives at our warehouse, and your quote uses those measurements.
Is the billable weight rounded? Yes. It's rounded up to the next whole pound for every courier except APC. See "Weight and size limits for shipments".
Still need help?
Our support team is available on weekdays from 09:00 to 17:00 ET at [email protected].