“Old news Nathan, talk about something I haven’t heard of”
Fair enough. Scroll to the bottom if you want to read about recent and upcoming changes, along with broad ideas of how we’ve helped companies lower their DIM weights.
For those who are new to parcel shipping - maybe you changed industries or recently took a promotion - hopefully this crash course helps it make more sense.
What is it and why not actual weight?
While actual weight was historically the only method to calculate shipping rates, it leaves out a key element — capacity. There is only so much space available on a truck, plane, or any other method of transportation.
Dimensional (or DIM) weight was implemented as a way to account for large but lightweight items.
For example: Say you have an 8-pound cast-iron skillet that fits in a 10×8×3 box (240 cubic inches) and a massive 2-pound blanket that fits into a 12×12×12 box (1,728 cubic inches). If only using actual weights, the carrier would charge only a fraction for the blanket as they would for the skillet….even though the blanket takes up over 7x as much space.
Quick note - the larger between DIM and actual weight is always used.
When was DIM weight implemented?
The use of DIM weight in shipping rates has undergone numerous evolutions over the years. Below is a timeline of major changes:
2007 — UPS & FedEx implemented DIM weight for domestic ground rates. But only for items over 3 cubic feet (5,184 cubic inches)
2015 — Both carriers removed the 3 cubic foot limit. Now DIM weight is factored on packages of all sizes
2017/2018 — Divisor was dropped from 166 to 139 (we’ll touch on what the divisor is below)
2019 — USPS implements DIM weight but only for priority mail and parcel express. Divisor of 166 though.
2025 — FedEx & UPS implement “fractional rounding.” AKA, rounding up to the nearest whole inch.
July 12, 2026 — USPS joins other carrier’s DIM criteria (139 divisor, fractional rounding, expands applicable categories, and overall crack-down)
How do I calculate DIM weight?
(Length × Width × Height) ÷ 139 = DIM Weight (lbs)
Measure: Take the Length, Width, and Height from the absolute longest points of the box—including any structural bulges or loose tape.
Round Up: Major carriers round fractional dimensions up to the nearest whole inch immediately. A 10.2-inch side is automatically treated as 11 inches.
The Divisor: Multiply those rounded dimensions to find the total cubic inches, then divide by the carrier’s standard DIM Factor (or divisor).
Come July 12’th when USPS hops on board, everyone will have a common divisor of 139
If you want a quick calculator: FedEx has a good one for DIM weight of parcels and UPS has a great one for the DIM weight of a multi-parcel or freight shipment.
The 2 big struggles I’ve seen:
1) “Fractional Rounding.” To put this in perspective: a 10.125 × 10.125 × 5.25 box has a DIM weight of 4 (rounded up from 3.87) BUT, you have to round up to an 11×11×6 box which has a DIM weight of 6 (rounded up from 5.22)
2) Internal vs. External dimensions. The industry standard to measure boxes is internal dimensions. But the carriers only care about the space the box takes up aka, the external dimensions.
To pull it together, I simplified the example of a 12×12×12 box earlier in this article. The internal dimensions equal 1,728 cubic inches (13lbs). The unfortunate reality is that the external dims of a 12×12×12 box are typically 12.375×12.375×12.625. Which means we must use 13×13×13 dims equaling 2,197 cubic inches (16lbs)
Recent & rumoured changes to DIM weight:
Oversized Charges — Starting at 10,368 cubic inches, additional charges will hit for these extremely large packages
3D Scanning — More and more primary hubs are adding 3D scanners to automatically measure packages in said hubs. The issue with this is that any bulges of a box could automatically trigger a higher DIM….even if it’s by an 1/32”
USPS’s “Crackdown” — USPS used to offer an alternative to the carriers by having a divisor of 166 and being more loose with their rules. They are rapidly changing to align with the rest of the industry.
A 125 Divisor? — 125 is already used by some international air carriers. The expectation is FedEx and UPS will at least test the waters with it at some point. The result would be an approximate 10% increase in billable weight.
Short of our own delivery fleet, it is what it is…right?
I’ve no idea who this person is other than he’s on The Voice. Just really liked the gif.
I think I’m going to keep using the above gif. Again, I have no idea who he is and can’t say he really looks like someone I’m grabbing a drink with….but he gives a certain vibe that I kinda like.
Anyway, yes and no. We can’t change the rules but we can change how YOU play the game. The market is always innovating.
If your parcel volume is small, maybe it’s as simple as implementing multi-depth boxes or adding a couple sizes if that sounds reasonable. OR, can you use a different material that is more flexible and not as bulky?
For higher volumes, automating is an option. Systems integrating robotics, vision, and AI can automatically identify the size of your product and cut a carton to the correct size.
Other options include moving from standard C-flute to B-flute corrugated, changing your void fill to a smaller footprint option, and auditing your current packaging design.
Of course, you can leverage the carriers against each other to negotiate your rate down but that will only go so far. Address the cause, not the symptom.
Want to learn more?
If you have questions, want to learn more, or maybe you want to do a deep dive on your DIM weights - reach out! You can reply to this email, book a conversation here, or reach out to me at the info below.
(812)244-9393 & [email protected]
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