Are Bubble Mailers Considered Packages? USPS Rules

Yes, bubble mailers are usually considered packages. USPS treats a padded mailer as a package (parcel) whenever it is more than 3/4 inch thick, rigid, or lumpy by more than 1/4 inch, which describes almost any bubble mailer with an item inside. Only a thin, flexible padded envelope holding flat contents can still mail as a First-Class large envelope.

The classification matters because it sets the service, the price and whether tracking is included. This guide walks through the USPS size rules for letters, large envelopes and packages, how they apply to bubble mailers, and how to ship one correctly.

How Does USPS Decide if a Mailpiece Is a Package?

USPS sorts mail into three shapes: letters, flats (large envelopes) and parcels (packages). The USPS Domestic Mail Manual sets maximum sizes for letters and flats, and anything that goes over the flat limits, or fails the flexibility and uniform-thickness rules, pays parcel prices.

In other words, a mailpiece doesn’t have to be a box to be a package. A padded envelope becomes one as soon as it is too thick, too stiff, or too uneven to count as a flat.

Why Are Most Bubble Mailers Considered Packages?

Bubble mailers usually fail the flat rules for three reasons. Any one of them is enough to make a mailer a package.

• Thickness. Bubble padding plus a phone case, jewelry box or folded shirt quickly goes past 3/4 inch.
• Uneven thickness. USPS requires flats to be uniformly thick, with bumps of no more than 1/4 inch. A small item inside a mailer creates exactly that kind of lump.
• Rigidity. Flats must be flexible. An envelope wrapped tightly around a box or a hard object isn’t a flat, even if it is thin.

That is why most sellers simply ship every bubble mailer as a package. Our USPS bubble mailer guide covers the free Priority Mail Padded Flat Rate Envelope and the mailer sizes that work best.

When Can a Bubble Mailer Ship as a Large Envelope?

A padded envelope can still mail as a First-Class Mail large envelope if it meets every flat rule: no more than 15″ × 12″, no more than 3/4″ thick, flexible, and uniformly thick. Flat contents like a few photos, a certificate or a thin booklet in a lightly padded envelope can qualify, as long as the total stays at or under 13 oz.

The trade-off is service. First-Class Mail large envelopes don’t include USPS Tracking, so if the mailer holds anything you’d need to trace, sending it as a package is safer. Our guide on whether you can write Do Not Bend on an envelope covers how to protect flat contents that must stay unfolded.

Which USPS Services Can You Use for a Bubble Mailer Package?

Once a bubble mailer counts as a package, you can send it with any USPS package service. These are the usual choices.

USPS Ground Advantage replaced First-Class Package Service in July 2023, and it is now the standard choice for light bubble mailers. Packages under a pound are priced in weight tiers up to 15.999 oz, and tracking is included. For prices by weight, see our guide on how much it costs to ship a USPS bubble mailer, or compare live prices in the ParcelPath rate calculator.

Can You Use Stamps on a Bubble Mailer?

You can pay for a bubble mailer package with stamps, but you have to cover the package price, not the letter price. A single Forever stamp only covers a 1 oz letter, and a bubble mailer that counts as a package needs Ground Advantage or Priority Mail postage.

There is also a drop-off rule: a stamped mailpiece that weighs more than 10 oz or is thicker than 1/2 inch must be handed to a Post Office clerk instead of being left in a collection box. Buying a label online avoids both problems, because the label shows the right service and price for the weight you enter. Our guide to eCommerce shipping explains how online sellers handle postage at volume.

How Do You Prepare a Bubble Mailer Package?

Preparation is the same as for a small box. These steps keep the mailer from tearing or getting stuck in sorting equipment.

1. Use the right size. The mailer should close flat over the item without straining the seams.
2. Seal it completely. Press along the whole adhesive strip and tape the flap if the mailer is full.
3. Add a return address. Put it in the upper-left corner. Our page on whether you can mail something without a return address explains why you shouldn’t skip it.
4. Place the label on the flattest area. Keep it off seams and away from the thickest lump of the contents.
5. Remove old labels. If you reuse a mailer, cover or remove every old address and barcode.

International bubble mailers also need a customs form, and USPS rules restrict items such as lithium batteries, liquids and aerosols, which may need different packaging.

Is a Bubble Mailer Package Insured?

It depends on the service. USPS Ground Advantage includes $100 of insurance, and Priority Mail includes up to $100 on most shipments, so a typical bubble mailer package is covered for loss or damage up to that amount. For higher-value items, buy additional coverage; our USPS insurance guide explains coverage and claims.

For sellers shipping many padded mailers, ParcelPath is free to use and gives up to 89% off USPS and up to 85% off UPS retail prices, with no subscription or per-label fee. It also offers Shipsurance coverage and free USPS pickups. Our guide to shipping for small businesses covers other ways to lower costs.

Frequently Asked Questions

Are bubble mailers considered packages or envelopes by USPS?

Most bubble mailers are considered packages. USPS treats a mailpiece as a package when it is over 3/4 inch thick, rigid, or has bumps over 1/4 inch, and a padded mailer with an item inside usually meets at least one of those conditions. Only a thin, flexible padded envelope with flat contents can still mail as a First-Class large envelope.

How thick can a bubble mailer be to count as a large envelope?

A bubble mailer can be no more than 3/4 inch thick to count as a large envelope, and it must also be no larger than 15 by 12 inches. It has to be flexible and uniformly thick, with no bump over 1/4 inch. If it fails any of those rules, USPS prices it as a package instead.

Do bubble mailers sent as packages get tracking?

Yes. When a bubble mailer ships as a package with USPS Ground Advantage or Priority Mail, USPS Tracking is included at no extra charge. A padded envelope that mails as a First-Class Mail large envelope does not include tracking, which is one reason many sellers ship every bubble mailer as a package.

Are padded envelopes the same as bubble mailers?

Mostly, yes. Bubble mailers are a type of padded envelope lined with air-bubble cushioning; other padded envelopes use paper fiber or foam. USPS doesn’t classify them by name. It looks at size, thickness, flexibility and how even the contents are, so the same rules decide whether either one is a large envelope or a package.

Sources

• USPS Domestic Mail Manual 101: Physical Standards for letters, flats and parcels
• USPS Ground Advantage: delivery time, weight tiers, tracking and insurance
• USPS Priority Mail: delivery time, insurance and Flat Rate envelopes

Find more guides in our Shipping Resources library.

Part of our Packaging guide. Related: Shipping Resources, Can You Write Do Not Bend on an Envelope?.