Maximum Box Dimensions for Shipping With USPS

Learn about the maximum box and poly mailer sizes for all the different USPS mail classes
maximum box dimensions
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Before you start shipping or start to create custom packaging for your business, it’s good to be aware of the maximum box dimensions to ship with the US Postal Service. We’ve listed all of that information below for the corresponding mail classes. First, you’ll need to know what the girth of your package is.

Table of Contents

How to Calculate the Girth of Your Package

To calculate your package’s girth, take the two smaller dimensions of your package (we’ll use Width and Height in this example), and add those two numbers together. Then, multiply that sum by 2 to get the Girth. The formula should look like this:

Girth = 2*(Width + Height)

Maximum Dimensions for Domestic Mail Classes

Priority Mail

  • Maximum Length + Girth: 108 inches

Priority Mail Express

  • Maximum Length + Girth: 108 inches

Priority Mail Cubic

  • Maximum Dimensions for boxes: No one dimension can exceed 18 inches, and total volume can’t exceed 0.5 cubic feet
  • Maximum Length + Width for poly mailers and envelopes: 36 inches

Ground Advantage

  • Maximum Length + Girth: 130 inches

Maximum Dimensions for International Mail Classes

First-Class Package International

  • Maximum Dimensions: 24″ in Length, Length + Width + Height: 36″

Priority Mail International

Priority Mail Express International

What About Minimum Dimensions?

They say good things come in small packages…but USPS does have a minimum package size requirement! When shipping a box, the minimum dimensions are 6x3x0.25″. This rule applies to any USPS mail class you decide to ship in.

USPS could technically reject your package if your box is smaller than those dimensions, but the chances of that happening are pretty rare. However, we always suggest using a box that’s at least as big as the minimum dimensions. If there’s no way for you to do that, we recommend putting the box into a small poly mailer envelope when you ship it.

Pro Tip: If you use free USPS boxes, you won’t have to worry about minimum dimensions at all…but you may have to worry about some new surcharges if you exceed certain dimensions! We’ll get into that below, but in the meantime, you can check out our guide that lists the dimensions of all the free USPS boxes if you’re in the market for some free packaging.

Beware of New Non-Standard Fees from USPS

In April 2022, USPS began imposing “non-standard fees” on packages, which are basically surcharges for being over a certain size. USPS never hit shippers with surcharges the same way UPS and FedEx did, but the Postal Service introduced these new surcharges in order to offset inflationary pressures from rising fuel and transportation costs.

The new USPS non-standard fees are as follows:

  • $4 if any length of your package exceeds 22 inches but is less than 30 inches
  • $15 if any length of your package exceeds 30 inches
  • $15 for packages greater than 2 cubic feet in volume
  • $1.50 for missing or incorrect dimensions that result in any of the above non-standard surcharges; you can think of this as an “overdraft” fee that USPS charges for imposing any of these non-standard fees

To learn more about these new USPS surcharges, check out our article: USPS Non-Standard Fees: A Guide to Understanding the New USPS Surcharges.

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  1. Rodney Gray

    Can I ship a box 40″ x 1 2″ x 4″ USPS

  2. Eva Barnas

    I have a box that is 18”L 10”H and 13”W. Can I mail it

  3. Keith

    I have a box 36.25 x21 x10.5
    Can I mail this in US mail

  4. Keith

    Price for a package 24 by 18 by 24. Lawrenceville nj to Houston tx

  5. SoLidWire

    Shouldn’t have to go to another page to determine the MAXIMUM ALLOWABLE WEIGHT 70 lbs.

    • Joyce

      I agree. This website is confusing for us older people.

    • Steven Chittick

      Pro tip incorrect. Post office surcharges on their priority mail small triangular shipping box and possibly others

      • Rockwell Sands

        Hi Steven, thanks for your comment! You’re right – I had yet to update the article to incorporate the new non-standard fees USPS introduced in April. I appreciate you pointing that out. I’ve updated the article to include those new surcharges!

  6. Mark

    Can I get a recliner in small packets delivered to me because that’s is coming To me by the 17 of this month

  7. Mark

    I just got a text from USPS they my package

  8. Rachel

    Mi pedido debio de llegar hace 15 días y ya tiene aparte de los 15 días, 2 semana en camino 🙆‍♀️Estoy desesperada

    • John Cleveland

      Need a. Need a box 19″by 15″

  9. Stephanie Marie

    Buenas yo tenía que recibir un paquete para el día 21 de septiembre y no me ha llegado nada al currier si es posible me pueden responder


      BUENAS TARDES YO TENIA QUE RECIBIR UN PAQUETE 17 de enero y no me ha llegado

  10. Joseph

    Hola . Tenía que llegar un paquete internacional a Hialeah ami casa pero sale que llego el 18 de septiembre y nunca se recibió nada .pueden ustedes verificar si esta en su oficina postal gracias nunero de pedido 17-07557-26855

  11. Moueenawan


  12. Jimoh sodiq abiola

    Pls some package was sent to me since 27th of July and till now , I haven’t received any call from USPS agent, when I tracked it , it shown that that package is Cincinnati since 30th of July and till now no upfront information about than the same Cincinnati, the tracking code start with ch, pls for how long am I going to expect this to be arrived advise me oool

    • Rockwell Sands

      Hi Jimoh – I’m sorry you’re on the hunt for this package! We don’t handle any packages at Shipping School, so we can’t tell you where it is. Your best bet at this point is to create a USPS account and submit a missing mail search request. You can do that here. I hope this is helpful!

  13. Miriam Rivera

    Do you have store at Staten Island NY?

    • Kathy

      I have heavy duty plastic containers 20x30x14 with lids. I will fill them to 45 lbs approx. can I ship them and approximate cost.

  14. Karen

    Can I use ISPS to ship box 18x18x18x18. ?

  15. Adaeze

    Hello! I want to ship some cards of good wishes and letters to my lover in Boston but I’m in Nigeria and River State currently. However,I never mailed once through USPS Internationally.

    Nevertheless, please tell me the cost for 5kg parcel following my location to my lover’s location.

    • Rockwell Sands

      Hi Adaeze – I’m sorry I can’t help more, but I only can point you in the direction of a quote for a shipment originating in the United States, not coming from Nigeria and going to the United States. You could try the UPS or FedEx website, assuming they have service in your country.

  16. Javier Gutiérrez

    I would like to know when item # CP064201552UA will arrive at Boca Raton wineries in Miami. Thank you

  17. Germain

    A list of the empty boxes for sale by USPS would allow me to plan shipping from Mata to France the goods and belongings that I decided to keep at the iccasion of my reasignment.^

    from Malta to France


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