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Dimensional Weight and USPS Shipping Rates

Jake Rheude

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In the summer of 2019, the US Postal Service changed the way it calculates shipping charges. USPS added dimensional weight pricing. USPS joined FedEx, UPS, and DHL in applying a size-based formula for oversized boxes. However, USPS has a higher DIM factor than most carriers, so its surcharge for large items is smaller (we break down the math below). And, in 2022, USPS introduced a new oversized shipping fee for “dimensional noncompliance.”

Understanding dimensional weight is critical for eCommerce fulfillment of large products or shipments. That knowledge will help you keep your USPS shipping costs as low as possible.

What is dimensional weight?

Dimensional or DIM weight is a formula that carriers use to determine the cost to ship an oversized package. DIM weight pricing allows carriers to incorporate size as well as weight into their price structure. After all, the number of packages that can fit on one truck or in one container depends as much on the size of the box as its weight.

If your package is heavy or small, you don’t need to worry about dimensional weight. You’ll pay for USPS shipping (or shipping with other carriers) based solely on the actual package weight. However, if you ship something relatively light in a large box, you may pay more than you expected.  Read on for examples of how DIM weight pricing can affect your USPS shipping costs.

Oversized packages

USPS oversized shipping

USPS box sizes

The changes that the US Postal Service instituted in June 2019 apply only to packages over 1 cubic foot in total area. That’s any box with a cubic area equivalent to or larger than 1,728 inches. To figure out whether your package falls into this category, multiply height x width x depth. If your total equals or exceeds 1,728 inches, your USPS shipment is subject to DIM weight pricing. USPS charges are always the greater of the actual weight or dimensional weight.

DIM weight pricing doesn’t affect the costs for USPS flat rate shipping. You can still ship any weight for a fixed price as long as your items fit into a flat rate box or envelope.

How to calculate DIM weight charges for USPS shipping

To make this easier, use our handy dimensional weight calculator.

To calculate USPS dimensional weight charges, use this formula:

H x W x D/166 = DIM weight

For example, let’s say you need to ship a box that weighs 2 pounds. Your box is 24” x 12” x 6”. Start by multiplying 24x12x6. If the total is at least 1,728, then calculate the DIM weight.

24 x 12 x 6 = 1,728

(24x12x6)/166 = 10.4

In this example, the dimensional weight of your package is higher than the actual rate. Your USPS shipping cost would reflect the 11-pound DIM weight rather than the 2-pound actual weight. If that same box weighed more than 10 pounds, you’d pay for actual weight rather than dimensional weight.

Now suppose you could fit your items into a slightly smaller box? If you fit them into a box that measures 24 x 10 x 6, that’s 1,440 cubic inches, so the box is under a cubic foot. In that case, your parcel isn’t subject to DIM weight charges on USPS shipping. You’ll pay to ship 2 pounds.

Red Stag Fulfillment applies its expertise in shipping oversized boxes to help our clients with situations like this. If a product is on the line between dimensional and weight-based pricing, we will look for ways to reduce your shipping costs, by finding a smaller box or through package consolidation.

USPS shipping

USPS fees for nonstandard and incorrectly measured boxes

In April 2022, USPS introduced new shipping charges for large packages. Any box with one side longer than 22 inches is subject to a $4.00 nonstandard fee because the Post Office needs to sort those boxes by hand. Packages with a dimension over 30 inches will be hit with a $15.00 surcharge and any box that’s more than 2 cubic feet will also have an extra $15 fee.

The USPS non-compliance fee applies to boxes larger than a cubic foot or with one dimension over 22 inches. If you don’t include your parcel dimensions when you print labels online or you give USPS the wrong dimensions, that’s an extra $1.50 fee.

These changes make USPS shipping less appealing for oversized eCommerce. Still, there may be situations where USPS is the best choice, even for large items. It’s another instance where a 3PL like Red Stag Fulfillment can help you optimize your shipping methods.

pick and pack fulfillment

What products are affected by dimensional weight charges?

If you use USPS for order fulfillment and your packages are smaller than 1 cubic foot or you ship heavy merchandise, your USPS shipping costs probably won’t include dimensional charges. However, if you send light objects in large boxes, DIM weight pricing could be a factor in your USPS shipping costs.

Some examples of products that are likely to be affected by DIM weight pricing are things that are more bulky than heavy. This could include products like a lightweight bike helmet. Fragile products, such as glass items or delicate sculptures, can also get hit with DIM charges. These items may need extra packaging to keep them safe during USPS shipping, so you might end up with a lightweight object in a large box.

DIM Weight and the Major Carriers

Both of the other major carriers, UPS and FedEx, also use DIM weight pricing. So, you won’t be able to escape DIM weight charges by switching from the USPS. However, the carriers have different DIM factors, and that can affect what you pay for oversize packages.

Let’s look at the example from above, the box that weighed 2 pounds. Using the DIM factor of 166 for USPS shipping, you had to pay for 11 pounds of postage. FedEx has a DIM factor of 139. The lower the DIM factor, the higher your costs. 

The formula to ship the 2-pound oversized box by FedEx looks like this:

(24x12x6)/139 = 12.4

Thus, you would pay for a 13-pound package if you shipped that item via FedEx.

UPS uses two DIM factors: 139 for daily rates and 166 for retail rates. Most eCommerce companies that use UPS have commercial accounts, so expect to use a DIM factor of 139, the same as FedEx.


There’s one more element to consider when you calculate DIM weight shipping: the rate that each carrier will charge you to deliver your package. The largest dimensional weight may not translate to the highest shipping cost. That is particularly true if one carrier starts out with a lower rate. Red Stag Fulfillment offers shipping discounts to its clients, to help you lower your shipping costs. And we’ve negotiated more favorable DIM factors with some carriers, to make oversized shipping more affordable.

How to save on oversized USPS shipping

USPS shipping may not be your first choice for sending oversized parcels, particularly with the surcharges introduced in 2022. However, if you do want to use USPS, there are a few strategies that may save you from dimensional weight pricing.

For example, instead of shipping your 2 pounds item in one large box, you could divide your shipment into two smaller boxes. If each box is under 1 cubic foot, it might cost you less to ship the two small boxes than a single large one. 

Another way to avoid or reduce dimensional pricing and surcharges is to use the smallest possible box to ship your items. Using a huge box surrounded by a large amount of infill isn’t the only way to safely ship fragile products. For example, fulfillment companies have innovative ways to pack and ship orders in the smallest possible box. Products that fit snugly in a box that’s just the right size need less infill to ship undamaged. 

fulfillment center packaging

How Red Stag Fulfillment helps eCommerce companies manage dimensional weight

At Red Stag Fulfillment, we have lots of experience shipping heavy items. We have shipped arcade games, bicycles, furniture, recreational equipment, and more. We have come up with some innovative ways to reduce the cost of FedEx, UPS, and USPS shipping for our clients.

Package consolidation

Suppose a customer orders a bicycle plus a pair of bike shorts and a jersey. The bicycle comes boxed from the factory, so we just need to label it during pick and pack fulfillment. We could put the gear in a small box and ship it separately. But, because a dimensional weight charge applies to the bike box, adding a little more weight won’t increase the shipping cost. If we can safely add accessories to the box, we ship part of the order at no additional charge. That’s the magic of package consolidation.

Lower DIM factor

Red Stag Fulfillment is a high-volume shipper, so we can negotiate discounted rates with the major carriers and offer discounted shipping to our clients. One of the things we negotiate is the DIM factor. If we can get a higher DIM factor with FedEx or UPS, that reduces the dimensional surcharge.

Error-free fulfillment

You don’t have to worry about surcharges to USPS shipping for missing measurements when you work with Red Stag Fulfillment. Our fulfillment guarantees promise that, if we make a mistake, we pay you $50 and we fix the problem. However, with Red Stag’s low error rates, you rarely have to worry about fulfillment mistakes.

If you’re looking for reliable, top-notch eCommerce fulfillment services for large or high-value products, Red Stag Fulfillment is an excellent choice. Just let us know what you need.

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