Don’t Use the USPS Website to Estimate DIM Weight

If you’ve visited USPS’ website since June 23rd to double-check your rates before you pay for postage, you may have noticed some odd discrepancies. Specifically, you may have seen that prices for Retail Ground are much cheaper on USPS’ website than prices for Parcel Select Ground on shipping software websites. The opposite is normally true; Parcel Select rates are typically much lower than Retail Ground. However, the DIM weight calculator on USPS’ website is currently misleading…so tread carefully!

Why You Shouldn’t Use USPS’ Website to Estimate DIM Weight Charges

This entire issue boils down to the fact that USPS doesn’t show DIM weight charges for Retail Ground on their website. As a result, when you check rates on the USPS website, you’ll see rates for Retail Ground without dimensional weight. So, to get that cheaper rate you see on USPS’ website, you would have to bring your box to the Post Office. Even though the service is technically comparable to Parcel Select Ground, USPS Retail Ground is only available at physical Post Office locations.

On the other hand, Parcel Select is a similar service, but it’s only available when you buy postage online through shipping software. So, this is a very rare instance of USPS actually charging MORE for postage purchased online through their partners than at the Post Office for virtually the same service. A fluke, if you will!

How to Properly Calculate DIM Weight

All in all, the moral of the story is not to rely on USPS’ website to estimate any DIM weight charges you might be hit with. You’ll have to calculate your package’s dimensional weights on your own. Luckily, it’s a fairly straightforward process.

To determine the dimensional weight of a package, multiply the package’s Height x Width x Length. Then, take that number and divide it by 166 to calculate the DIM weight. Here is that equation all laid out:

DIM = (HxWxL)/166

When determining the price of a package, USPS (and all the other shipping carriers) will charge for postage based on whichever weight is greater: the dimensional weight or the actual weight.

A Quick Example

Let’s say your box is 13x13x13″. In this case, 13 x 13 x 13 = 2197 / 166 = 13.23 lbs. That means if your package’s actual weight is less than 13.23 pounds, you’ll end up paying for the 13.23 pound rate instead.