You can ship large packages to a PO Box through USPS as long as they stay within the Postal Service’s mailing limits: 70 pounds maximum and 130 inches in combined length and girth. If the package is too big to fit inside your assigned box, USPS puts it in a parcel locker or holds it at the counter for you. Private carriers like UPS, FedEx, and DHL won’t deliver to a standard PO Box address at all, though a USPS feature called Street Addressing works around that at participating post offices.
USPS Size and Weight Limits
Every domestic package USPS accepts must weigh 70 pounds or less. Anything heavier is nonmailable, no matter which service you use.1USPS. Parcel Size, Weight and Fee Standards
Size limits depend on the service. Priority Mail and Priority Mail Express top out at 108 inches in combined length and girth. USPS Ground Advantage goes up to 130 inches, though anything between 108 and 130 inches gets an oversized surcharge. Girth is the distance around the thickest part of the package, measured perpendicular to the longest side. For a rectangular box, that’s (height × 2) + (width × 2). Add the length and you have the combined measurement USPS cares about.2USPS. How to Prepare and Send a Package
In practical terms, 130 inches covers most things a person would ship. A four-foot-long box that measures 18 inches on each side comes out to 48 + 36 + 36 = 120 combined inches, comfortably under the ceiling. Where people run into trouble is with oddly shaped items like golf bags, skis, or oversized framed artwork.
What Happens When the Package Won’t Fit Your Box
PO Boxes come in five sizes, and even the largest (roughly 12 by 22.5 inches) can’t swallow a shipping box of any real depth. So when a package clears USPS mailing standards but won’t physically fit, the clerk uses one of two fallback methods.3United States Postal Service. PO Boxes
Parcel Lockers
The first option is a parcel locker: a larger compartment sitting near the PO Boxes in the same facility. The clerk drops your package inside, locks the locker, and places the key in your PO Box. You open the locker, take your package, and leave the key inside. The locker relocks and gets reassigned to the next customer who needs it. If you don’t retrieve the package within about seven business days, staff may move it to the retail counter.4United States Postal Service. Customer Agreement for Premium PO Box Service Additional Services
Counter Pickup
If the package is too large even for a parcel locker, or no locker is available, USPS holds it behind the counter and leaves a notification slip (PS Form 3849) in your PO Box. The slip tells you what’s waiting and how to pick it up. Bring a valid photo ID during business hours. You can also authorize someone else to pick up on your behalf by signing the appropriate section of the form and writing in their name.5USPS. PS Form 3849 Redelivery Notice
USPS holds items at the counter for a limited window before returning them to the sender. Inbound Express Mail is held for 15 days. Standard packages generally follow a similar timeline, though the exact retention period can vary by mail class and post office. Don’t let a slip sit in your box for a week and a half without acting on it.
Signature-Required Packages
Packages that need a signature create an extra step, because nobody is standing at the box when the mail arrives. By default, USPS leaves a notification slip in your box and you sign for the package at the counter.
The workaround is a free service called Signature on File. Once you opt in through the Premium PO Box Service agreement, USPS uses your stored signature for qualifying mail and places the item directly in your box or a parcel locker. It covers Priority Mail Express, insured mail valued over $500, and Signature Confirmation shipments. It does not cover Registered Mail, Certified Mail, or items with Restricted Delivery, which still require a counter pickup.4United States Postal Service. Customer Agreement for Premium PO Box Service Additional Services
Why UPS, FedEx, and DHL Can’t Deliver, and How to Get Around It
UPS, FedEx, DHL, and Amazon’s own delivery network all require a physical street address. A PO Box number doesn’t qualify, so packages shipped through these carriers to a standard PO Box address get returned to the sender. This is the single biggest frustration for PO Box holders who order from retailers that default to non-USPS shipping.
Street Addressing
USPS offers Street Addressing at participating locations. When you activate it, senders can use the post office’s street address with your PO Box number in place of an apartment or suite number. Private carriers deliver to the post office building, and USPS staff sort the package to your box or a parcel locker like any other piece of mail.3United States Postal Service. PO Boxes
To turn it on, you sign the Customer Agreement for Premium PO Box Service at your post office and pay for the service. Not every location offers it, so check availability before counting on this option. The USPS post office locator at usps.com/locations lets you search by ZIP code and filter for PO Box services. Packages delivered this way still have to comply with USPS mailing standards once they enter the postal system, meaning the same 70-pound and 130-inch limits apply.6USPS PostalPro. Premium PO Box Service Street Addressing
Private Mailbox Services
If your post office doesn’t offer Street Addressing, a private mailbox from a retailer like The UPS Store gives you a real street address with a suite number and accepts packages from every carrier. These services also handle package notification, mail holding, and sometimes mail forwarding. Monthly rental fees vary by location and mailbox size. The tradeoff is an ongoing cost on top of whatever you already pay for a PO Box, so it makes the most sense if you receive frequent shipments from non-USPS carriers.
Picking a Box Size That Cuts Down Counter Trips
All PO Boxes share a depth of about 14.75 inches, but the opening dimensions differ enough to change how often you’ll be picking up from a locker or counter:
- XS (Size 1): 3″ × 5.5″ opening. Letters only.
- S (Size 2): 5″ × 5.5″. Fits one Small Priority Mail Flat Rate Box.
- M (Size 3): 5.5″ × 11″. Large envelopes flat, plus a couple of small flat-rate boxes.
- L (Size 4): 11″ × 11″. Small and medium flat-rate boxes with room for letters.
- XL (Size 5): 12″ × 22.5″. Multiple packages at once.
Not every post office carries all five sizes, and pricing varies by location. If you regularly receive packages, starting with at least a Medium saves repeated trips. USPS also reserves the right to require an upgrade if your mail exceeds the box’s capacity on 12 out of any 20 consecutive business days.3United States Postal Service. PO Boxes
Knowing a Package Is Coming
USPS Informed Delivery works with PO Box addresses and is worth setting up. The free service sends daily email digests with grayscale images of incoming letter-sized mail and tracking updates for packages headed your way. You’ll know a package is waiting before you drive over.7United States Postal Service. Informed Delivery for Business Mailers
If you need to redirect a package already in transit, USPS Package Intercept can reroute eligible items before delivery for $19.45 plus any applicable Priority Mail postage. One limit worth knowing up front: items cannot be redirected to a PO Box through this service.8United States Postal Service. USPS Package Intercept