USPS Services and Packaging Requirements in 2025

Businesses typically choose between three main shipping partners—USPS, UPS, or FedEx. For many, USPS presents the cheapest option, especially for those who primarily ship lightweight, similarly sized items.

EcoEnclose is proud to work with USPS for many of our shipments. Besides offering excellent services, their pricing for our samples and smaller orders is hard to beat. Over the years of partnering with USPS, we’ve learned much about how to package things effectively, the best mailer sizes, and the mailers to avoid.

To share what we’ve learned, we’ve broken down some of the most important things to know regarding packaging for USPS based on our research and experiences. These are all updated according to the latest regulations as of January 2025.

Specifically, we cover:

• Categories of shipments—what qualifies as a letter versus a flat versus a parcel
• Minimum packaging standards for each shipment category
• USPS standard shipping services

• USPS-friendly shipping bags, boxes, and mailers from EcoEnclose

Souce: Unsplash

Parcels are mailings that are:

• At least 3 inches high x 6 inches long x ¼-inch thick.

• No more than 108 inches in length and girth combined (a combined 130 inches is allowed for USPS Ground Advantage). Length measures the longest dimension, and girth is the distance around the thickest part (perpendicular to the length).

• No more than 70 pounds.

These are always made of paper. Any non-paper envelope (such as a poly mailer) shipped as a "letter" would be considered non-machinable and subject to additional charges. This includes additions like strings, buttons, or clasps. Loose items within paper envelopes may also make the letter nonmachinable, resulting in additional fees.

These can be made of paper, plastic bags/polyethylene, flat corrugated boxes, or cloth.

Polyethylene mailers, like our USPS-friendly Poly Mailers, must be at least 2 mils* thick for shipments up to 5 pounds and 4 mils thick for shipments up to 10 pounds (and are not acceptable for shipments over 10 pounds). When poly mailers are used, their overhang should not exceed 0.5 inches when the package is lying flat and have a uniform thickness. Any paper used for paper bag packaging or paper wrap packaging must be 50 pounds in strength. Finally, they should be able to bend. Otherwise, they will be considered a parcel.

*1000 mils = 1 inch.

Note: Poly shipping bags are another plastic bag shipping solution we offer, but these are used for inner packaging only.

These are usually made of corrugated shipping boxes.

Parcels over ¾-inch thick (or exceed other dimensions required to qualify as a large envelope/flat) but still relatively thin could be packaged in expandable paper envelopes, poly mailers/plastic bags, paper bags or wrap, or even cloth. Poly mailers for USPS must be at least 2 mils thick for shipments up to 5 pounds and 4 mils thick for shipments up to 10 pounds. They are not acceptable for shipments over 10 pounds. Any paper used for USPS shipping bag packaging or paper wrap packaging must be 50 pounds in strength.

A non-machinable and/or irregular parcel surcharge may be applied if the above standards aren’t met, if maximum weights and dimensions are exceeded, or if a package is oddly shaped or irregular. This is why it’s always best to purchase packaging that you already know is USPS-compliant.

Souce: Unsplash

USPS has five main categories of shipping services relevant to an eCommerce business. The actual price of shipping will vary based on the service selected, the mailing type (letter, large envelope, or parcel), the exact weight and dimensions of the mailing, and the distance it will travel. Let’s take a look.

This service is typically the most inexpensive shipment option and is always the optimal choice if you’re shipping something lightweight that fits in an envelope or flat. Pricing is not dependent on how far the mail travels, making it an ideal fit for companies that offer free shipping on light items—you’ll know your shipping costs ahead of time. We’d like to note that, as of July 2023, you can no longer send packages through First-Class Services. You must use Ground Advantage, which is detailed below.

Here’s a rundown of First Class services:

• Types of packages: Letters, large envelopes, or flats

• Weight limits: 3.5 ounces or less for letters, 13 ounces or less for large envelopes, flats, or parcels

• Includes: Forwarding and return services

• Cost: Based on weight and shape

This service offers weight flexibility within quick delivery times: 1 - 3 business days anywhere in the United States. Unlike First Class, Priority Mail shipments are priced based on distance and are calculated by the number of shipping zones the package has to cross to reach its final destination. It’s important to note that it cannot exceed 108 inches in combined weight and girth.

Here’s the rundown:

• Types of packages: Letters, large envelopes, flats, and parcels

• Weight: Any shipment under 70 pounds, any mailing over 13 ounces (or a letter over 3.5 ounces)

• Includes: USPS Tracking, forwarding services, and return services, Free Package Pickup, up to $100 of insurance

• Cost: Based on distance, weight, and shape

This is the fastest mail service offered by USPS. It provides guaranteed 1-day or 2-day expedited service by 3 pm for any mailable matter. In many locations, it’s also offered 365 days a year. This makes it an excellent option for orders that might have been damaged or incorrect and need to be replaced ASAP, emergency orders, expensive products, or if you’d like to go above and beyond for your customers.

Here’s the rundown for Priority Express:

• Types of packages: Letters, large envelopes, flats, and parcels.

• Weight: Any shipment under 70 pounds

• Includes: $100 of insurance coverage, money-back guarantee for late shipment, proof of delivery signature record, Free Package Pickup

• Cost: Based on weight and distance

• Note: As of August 1, 2023, USPS will no longer offer a money-back guarantee for packages addressed to or from Alaska or Hawaii, except if the package is lost.

Media Mail is USPS's cost-effective way to send packages containing media and educational materials (typically quite dense and heavy). Only books (at least eight pages), printed music and test materials, video and sound recordings, printed educational charts, medical loose-leaf pages, binders, or computer-readable media can be sent this way. Video games, computer drives, and digital drives are not eligible for Media Mail prices.

Here’s the rundown:

• Types of packages: Envelopes, flats, or parcels containing accepted media items

• Weight: 70 pounds or less

• Cost: Based on weight

• By shipping via Media Mail, you consent to have your package contents inspected and verified.

Historically referred to as Parcel Post, Parcel Select, or Retail Ground, this shipping class is for small and large packages, thick envelopes, and tubes. It promises domestic delivery within 3 - 5 business days. If you have a flat package or envelope that doesn’t meet the requirements for First Class, you’ll have to opt for this service. Because it’s a ground service, it’s the primary option for those sending hazardous materials that cannot be transported by plane.

• Types of packages: Parcels or large envelopes being treated as packages

• Weight: 70 pounds or less

• Included: $100 insurance, Free Package Pickup

• Cost: Start at $5.00 at a Post Office location. Based on weight, size, and shape.

To learn more about USPS's shipping services for small businesses, check out their Business Mail 101 Portal. Or, check out their handy chart comparing services.

First-Class Mail prices increased in July 2024, but USPS has confirmed that they will not increase in 2025. Here are the current First-Class Mail prices.

This year, USPS raised its shipping services prices, including an approximate 3.2 percent change for Priority Mail, a 3.9 percent increase for USPS Ground Advantage, and a 9.2 percent increase for Parcel Select. Even with the price increases, it offers competitive pricing and excellent services for eCommerce businesses. USPS shipping rates are determined by rate and delivery distance.

 The changes, valid as of January 19, 2025, are as follows.

Here's a handy chart to give you a rough estimate of what your package might cost based on its weight. Please note that these only outline the cost of sending a standard package in Zone 1. The prices go up for large packages over 12 inches in any dimension or shipments sent over longer distances

You can check out a full list of USPS prices here. To determine the price for a specific package, check out the official USPS shipping rates by weight charts or use the USPS shipping rates calculator.

USPS offers shipping boxes, envelopes, mailers, and shipping materials, including free and flat-rate options. While this can be ideal for individual use, eCommerce businesses should consider using their shipping materials instead.

Investing in USPS-friendly shipping bags, boxes, mailers, and postal packaging allows you to enjoy USPS shipping services while offering a top-notch unboxing experience to your customers. Sure, using USPS’s free shipping boxes may save some money, but you won’t be able to customize them. When your customers receive their products, it will feel like they’re receiving an order from an individual rather than an established business.

Furthermore, custom postal packaging puts you in control. You can choose the shipping materials that perfectly protect your products without too much filler. On top of this, you can choose USPS-friendly mailers and shipping boxes that align with your sustainability goals.

Although USPS is working toward its sustainability goals, it could do better. Opting for your postal packaging allows you to partner with a packaging company as committed to sustainable choices as you are.

Check out USPS-friendly shipping bags, poly mailers, shipping boxes, and more here at EcoEnclose.

Although USPS has its own sustainability goals, you can still do your part to minimize your shipment's environmental impact even further. Here are our tips.

 Opt for slower delivery services: Air freight has a higher carbon footprint than ground, so the environmental cost of shipping an item too quickly can be significant. Furthermore, slower ground delivery times provide space to optimize delivery routes for a lower carbon footprint.

One of USPS’s goals is to increase the recycled content of their packaging to 74% and increase the recyclability of their packaging to 88%. Although these goals are commendable, they could be better. Instead of choosing their ReadyPost mailers, invest in 100% recycled (or as recycled as possible) and USPS-friendly recyclable mailers.

• Choose eco-friendly mailers: One of USPS’s goals is to increase the recycled content of its packaging to 74% and the recyclability of its packaging to 88%. Although these goals are commendable, they could be better. Instead of choosing their ReadyPost mailers, invest in 100% recycled (or as recycled as possible) and USPS-friendly recyclable mailers.

• Reduce returns: Returning deliveries increases the carbon footprint of eCommerce. This poses a dilemma for eco-conscious eCommerce companies who also want to offer quality service to their customers. Minimize your returns by avoiding flash sales that encourage impulse buys, including detailed product descriptions with thorough sizing information, and utilizing pop-ups that educate customers about the environmental footprint of returns to ensure that they’ve fully inspected their order. If a return happens, use packaging that can be reused for the return to minimize waste.

• Develop packaging end-of-life strategies: Although you cannot control what your customers do with your packaging, you can encourage them to dispose of it most sustainably. Provide information on the packaging that outlines whether it can be recycled or composted, use social media campaigns to educate your customers, or offer discounts to customers that tag your company in a picture of their packaging in the compost or recycling bin.

Shop our suite of recycled mailers and check out a few mailer options below to get started.

Feeling overwhelmed? Contact us today. We are happy to help!

Upcycled newspaper sandwiched between recycled Kraft paper. Ideal for shipping fragile items. 100% recycled, 25% post-consumer waste.

For mailer size 10.5" x 15"
- Package weight: 13 oz or more
- Shipping service: Priority
- Package type: Flat/Envelope

Ready to ship  |  Min. 10 units
Customizable  |  Min. 500 units

EcoEnclose is the leading sustainable packaging company that provides eco-packaging solutions to the world’s most forward-thinking brands.

We develop diverse, sustainable packaging solutions that meet our rigorous research-based standards and customers’ goals. We drive innovative packaging materials to market and consistently improve the circularity of existing solutions.