You are here: Home / 2023 / June / 28 / Flat Rate?

Flat Rate?

Published on by

I mailed some packages to The Girls the other day, two in USPS Flat Rate boxes, and one whose rate was calculated based on weight and size. I got to thinking about the cost effectiveness of flat rate boxes. Here’s what I discovered at https://goshippo.com/blog/usps-priority-mail-vs-usps-flat-rate/.

Almost finished writing this and I realized the flat rates at that site are out of date. Here are the USPS rates as of today: Small box (dimensions below) $10.20; Medium (two different configurations, same volumes) $17.10; Large $22.80.

I’m just going to assume that though the absolute numbers are incorrect, the rates increased across the board, so the configuration of which is more economical remains the same.

You’ll first need to determine the zone (refers to distance traveled). You can enter pairs of zip codes here, and it will calculate the zone.

I usually order the 4-box assortment of free flat rate boxes. The small is pretty small. It’s total volume is 82.6 in3. For zones 1-5, only packages of the weights not in blue are cheaper to ship regular Priority Mail.

Note that your box may not be the exact size of a USPS small box. Here is where you begin calculating the cost of sending your box using Priority, not flat rate–after a few questions you’ll eventually input the size of the box.

Here are the thresholds for the medium flat rate boxes. USPS has two different medium flat rate boxes:

11.25″ x 8.75 x 6 = 590.625 in3

12.125″ x 12 x 3.5 = 593.25 in3

Unless a box (of about 590 in3) weighs more than 10 lbs, it’s less expensive to send Kat something, who is zone 4 distance from me, using regular priority. Daughter C and Miss M’s packages, in zone 5, need only be more than 6 lbs.

The large flat rate box is 900 in3.

Something’s either got to be going a long way, or weigh a lot for this to really pay off.

Note that the maximum weight for all size boxes is 70 lbs.

Final note–none of these calculations factor in the cost of boxes. I’m assuming most folk have a plentiful supply of free boxes, courtesy of that big store in the sky.

2 Responses

  1. You did a great job figuring out effective weight decisions on flat rate. I’ve felt like my head was going to explode trying to figure it out. Last Christmas I asked our postal clerk to weigh things and tell me prices before I boxed them. I took my tape and scissors and markers with me and packed them in the lobby.

    1. Thanks. I started doing it by hand then thought, surely someone on the internet has looked at this since there are so many small at-home type people mailing things as part of an extra cash business.

      It was an interesting exercise b/c they really get you on the psychological side of things. Especially the large box. It’s big, gonna coast a lot. When really it’s the least efficient option–unless you’re sending books or rocks!

Comments are closed.