What is First-Class Mail Postage and Why It Matters

If you’ve ever wondered what is first class mail postage, think of it as the go-to USPS mailing option for sending letters, postcards, flats, envelopes, and lightweight packages quickly and affordably. It’s one of the most widely used USPS services because it combines low cost, fast delivery speed, and a range of options for both personal correspondence and business mail.

With first class mail, you can send:

• Letters up to 3.5 ounces
• Envelopes
• Large envelopes (also called flats) up to 13 ounces
• First class packages up to 13 ounces for retail, or 15.99 ounces for commercial pricing

Most items arrive within 1–5 business days, making it an affordable and easy way to reach customers, clients, or friends without paying for priority mail. First-Class Mail is often the most affordable way to send letters, postcards, envelopes, and lightweight packages compared to other USPS options. For time-sensitive materials like invoices, event invitations, or lightweight eCommerce orders, first class mail service offers a balance of speed and cost-effectiveness.

It’s also a flexible option—whether you’re mailing a postcard, an invoice, or a small package in a poly mailer or plain or branded box, you can tailor the service to fit your needs.

💡 Want to explore how LettrLabs can help you design and send personalized postcards or letters using USPS First Class? Check out our direct mail formats to see your options.

Key Takeaways About First Class Mail

When it comes to first class mail, here are the essentials you need to know:

• Weight Limits – First class mail letters can weigh up to 3.5 ounces. First class package service covers items up to 13 ounces for retail customers, and 15.99 ounces for those using commercial prices. Anything heavier moves into priority mail territory.
• Delivery Speed – Expect 1–5 business days for domestic delivery, with local mail often arriving faster. First-Class Mail also serves associated territories such as Puerto Rico, Guam, and other U.S. territories, ensuring broad delivery coverage.
• Service Types – The USPS offers different first class services, including standard letters, first class mail postcards, large envelopes, and lightweight packages.
• International Options – You can send lightweight packages globally through first class package service international, and letters/postcards via first class mail international.
• Tracking – Standard letters and postcards do not include USPS tracking by default, but first class package shipments do. Additional extra services like Certified Mail can be added for more delivery confirmation.
• Automatic Forwarding & Returns – USPS includes address forwarding and “return to sender” services at no extra charge.

For small businesses, eCommerce stores, or marketers, these features make first class mail service a cost effective way to maintain consistent outreach without committing to bulk marketing mail minimums or paying extra fees for every delivery.

💡 If you’re running a campaign and want to combine the reach of First Class with data-driven targeting, LettrLabs’ direct mail automation can help you send at the right time, to the right audience—automatically.

What is First Class Mail Used For?

First class mail is designed for sending items that need reliable delivery speed without the premium price tag of priority mail. Businesses, organizations, and individuals use it for a wide range of purposes, including:

• Personal correspondence – Letters to friends or family, holiday cards, thank-you notes, and other personalized messages.
• Personalized business correspondence – Contracts, invoices, quotes, and proposals where professionalism and timely delivery are key.
• Postcards letters & mailing postcards – Both personal and marketing messages can be sent as postcards, provided they meet the USPS minimum size and maximum size rules.
• Large envelopes (flats) – Ideal for certificates, reports, or marketing brochures that can’t be folded.
• Lightweight packages – Sending small products, samples, or merchandise under 13 ounces (retail) or 15.99 ounces (commercial).
• Poly mailers, plain or branded box shipments – Flexible packaging options make it easy to match your brand style while meeting USPS first class mail requirements.

Items shipped via First-Class Mail benefit from reliable delivery and cost savings, making it a trusted option for shipping packages, letters, and flats.

One of the main advantages of first class mail service over usps marketing mail is that there’s no minimum number of pieces required. You can send just one letter or package, or hundreds, without needing a permit. This makes it perfect for ecommerce winback campaigns, seasonal greetings, or quick one-off communications. Shipping packages through First-Class Mail is ideal for small businesses and individuals who need a balance of speed and affordability.

💡 If you want to pair First Class delivery speed with beautifully designed pieces, explore LettrLabs’ handwritten mailers for a personal touch that stands out in any mailbox.

Is First Class Mail the Same as Regular Mail?

Many people ask if first class mail is just another term for “regular mail,” and the answer is — yes, but with a few specifics.

When you drop a stamped letter or postcard in the mailbox, the postal service processes it as first class by default. This covers letters, postcards, envelopes flats, and first class packages that meet USPS size and maximum weight requirements.

Regular mail in USPS terms is simply class mail that falls into the first tier — meaning it gets faster delivery speed than usps marketing mail or media mail, but less priority than priority mail or priority mail express.

That’s why first class services are often the default choice for personal communication, small business shipments, and official documents. It’s reliable, affordable, and includes extra benefits like free address forwarding and “return to sender” services.

💡 If you’re looking to send regular mail but want to make it stand out, check out LettrLabs’ printed letters for professional, USPS-ready designs you can customize.

Types of First Class Services

The USPS offers several first class services depending on what you’re mailing. The main categories are letters, postcards, large envelopes (flats), and first class package service. Each has its own minimum size, maximum size, maximum weight, and packaging rules. For First-Class Package Service, shipping labels are required and can be purchased online or at the post office.

First Class Mail Letters

First class mail letters are the most common option, used for personal correspondence, typewritten material bills, invoices, or legal notices.

• Weight limit: Up to 3.5 ounces
• Dimensions: Minimum size is 3.5” x 5”; maximum size is 6.125” x 11.5”
• Thickness: Between 0.007” and 0.25”
• Must be rectangular and machinable to avoid extra fees

If your letter exceeds the maximum size or weight, it’s considered a flat instead.

First Class Mail Postcards

First class mail postcards are a low-cost way to send postcards letters for marketing or personal use.

• Minimum size: 3.5” x 5”
• Maximum size: 4.25” x 6”
• Thickness: 0.007” to 0.016”
• Oversized postcards are charged at letter rates

These are ideal for mailing postcards with offers, event announcements, or quick customer updates.

Large Envelopes (Flats)

Envelopes flats are used for items like certificates, booklets, or marketing brochures that can’t be folded.

• Maximum weight: 13 ounces
• Minimum size: 6.125” x 11.5”
• Maximum size: 12” x 15”
• Thickness: 0.25” to 0.75”

Anything beyond these limits is classified as a package.

First Class Package Service

The first class package option is for lightweight packages and small merchandise, specifically designed for shipments weighing less than one pound—making it ideal for small, inexpensive packages.

• Retail limit: Up to 13 ounces
• Commercial prices: Up to 15.99 ounces
• Suitable for shipping in a poly mailer, plain or branded box, or usps branded packaging
• Includes USPS tracking at no extra charge
• Perfect for ecommerce sellers needing to ship lightweight packages cost-effectively

💡 If you want to send packages with personalization that drives customer engagement, LettrLabs’ printed postcards and handwritten mailers can be paired with First Class for maximum impact.

First Class Mail Service vs Priority Mail

While first class mail service is one of the most popular USPS shipping methods, it’s not always the best choice for every mailing. The main difference between first class and priority mail comes down to weight, delivery speed, and handling priority.

Here’s how they compare:

• Weight Limits – First class mail allows letters up to 3.5 ounces and packages up to 13 ounces (retail) or 15.99 ounces (commercial prices). Anything heavier must be sent via priority mail, which can handle up to 70 lbs.
• Delivery Speed – First class services typically arrive in 1–5 business days, while priority mail is usually delivered within 1–3 business days.
• Handling Priority – USPS treats priority mail as a higher priority class, meaning it’s sorted and delivered before first class.
• Included Features – Priority mail includes insurance (up to $100 domestic), while first class package service only offers tracking unless you pay extra fees for additional coverage.
• Best Use Cases – Choose first class for lightweight shipments, postcards, and letters. Go with priority mail for heavier items, time-sensitive deliveries, or shipments requiring included insurance.

For certain scenarios, USPS ground advantage or retail ground can be more economical than priority mail, but they’re slower than both first class and priority.

💡 If you’re not sure which USPS option is best for your campaign, LettrLabs’ direct mail automation can help you pick the most efficient method while streamlining the entire mailing process.

First Class Mail Delivery Time

The estimated delivery time for first class mail is typically 1–5 business days for domestic shipments. Local deliveries often arrive in 1–3 business days, while coast-to-coast or rural deliveries can take the full 5 business days.

Factors that affect delivery speed include:

• Distance – Mail traveling across multiple USPS regions takes longer than in-state deliveries.
• Weather – Severe storms, floods, or snow can slow down transportation and sorting.
• Holidays & Peak Seasons – During periods like Thanksgiving through New Year’s, post office backlogs can add delays.
• Address Accuracy – Incorrect ZIP codes or incomplete addresses can cause rerouting, which delays arrival.
• Volume Surges – Seasonal campaigns or national events can increase processing times.

USPS does not guarantee delivery dates for first class services, so if you need guaranteed speed, priority mail express may be the better choice.

💡 If you’re planning a time-sensitive campaign, LettrLabs’ tracking and analytics tools can help you monitor delivery performance and adjust send dates for maximum impact.

First Class Mail Weight, Size & Shape Requirements

To qualify for first class mail service, your item must meet USPS minimum size, maximum size, and maximum weight guidelines. Your package's weight is a key factor in determining the correct postage and service eligibility. Even a small deviation can change your postage rate or move your item into a different class.

Letters

• Weight: Up to 3.5 ounces
• Minimum size: 3.5” x 5”
• Maximum size: 6.125” x 11.5”
• Thickness: 0.007” to 0.25”
• Must be rectangular; irregular shapes may require extra fees

Postcards

• Minimum size: 3.5” x 5”
• Maximum size: 4.25” x 6”
• Thickness: 0.007” to 0.016”
• Oversized postcards are charged at letter rates

Large Envelopes (Flats)

• Maximum weight: 13 ounces
• Minimum size: 6.125” x 11.5”
• Maximum size: 12” x 15”
• Thickness: 0.25” to 0.75”
• If it exceeds size or weight limits, it becomes a package

First Class Package

• Retail limit: Up to 13 ounces
• Commercial prices: Up to 15.99 ounces
• Maximum combined length for retail packages: 108” (length + girth)
• Must be in an approved container like a poly mailer, plain or branded box, or usps branded packaging

💡 Not sure if your piece meets USPS rules? LettrLabs’ direct mail formats guide walks you through dimensions, shape requirements, and best practices so your mail is always USPS-compliant.

Cost and Commercial Prices

The cost of first class mail depends on what you’re sending, its package’s weight, and whether you qualify for commercial prices. Businesses and high-volume mailers can access discounted rates through commercial pricing or approved mailing platforms, helping them save on shipping costs. USPS offers two main pricing tiers:

Retail Rates

• Letters: Starting at the price of a Forever Stamp (currently $0.68) for the first ounce, with extra fees for each additional ounce.
• Postcards: Starting at $0.53 for standard sizes; oversized postcards are charged at letter rates.
• Large envelopes (flats): Starting at $1.39 for the first ounce.
• First class package service: Starting around $4.75 for packages up to 4 ounces, with prices increasing by weight and distance.

Commercial Prices

If you send mail in volume and meet USPS preparation requirements (like presorting and CASS-certified addresses), you can access discounted commercial prices.

• Letters: Often several cents cheaper per piece.
• First class package: Can be $0.50–$1.00 cheaper than retail for the same weight.
• Rates apply for packages up to 15.99 ounces instead of the 13-ounce retail limit.

Ways to Save

• Presorted first class mail can reduce costs by up to 20% when mailing 500+ pieces.
• Using automation tools to prepare and address mail correctly avoids extra fees for manual processing.
• Choosing the right packaging (like poly mailers instead of boxes) can reduce weight and save on postage.

💡 Want to know how First Class pricing stacks up against other USPS options? Check out LettrLabs’ cost of a direct mail campaign guide for a detailed breakdown and ROI tips.

Tracking and Extra Services

With first class mail, USPS tracking depends on the type of item you’re sending.

• First class package service (both retail and commercial) includes USPS tracking at no extra cost. You’ll get a tracking number and tracking information updates until delivery.
• Letters, postcards, and flats don’t include tracking by default. To monitor delivery, you’ll need to purchase extra services like Certified Mail, Registered Mail, or Signature Confirmation.
• For lightweight packages, tracking is automatically included — making it a reliable way to send eCommerce orders or customer gifts without paying extra fees.

Other extra services you can add to first class services include:

• Return receipt – Get proof that your item was delivered and signed for.
• Collect on delivery – Recipient pays for the item at delivery.
• Insurance – Covers loss or damage for eligible packages.
• USPS branded packaging – Free supplies for certain shipping categories, though not required.

💡 If you want deeper insight beyond USPS tracking, LettrLabs’ tracking and analytics tools give you campaign-level reporting on delivery rates, engagement, and ROI.

How to Send First Class Mail

Whether you’re mailing letters, postcards, envelopes flats, or a first class package, the process is straightforward. Here’s how to do it right and avoid extra fees.

1. Prepare Your Mail Piece

• Choose the correct packaging — poly mailer, plain or branded box, or envelope that meets USPS minimum size and maximum size requirements.
• For personalized business correspondence, use professional stationery or branded materials to boost impact.

2. Address It Correctly

• Write or print the residential or commercial address clearly.
• Include return address in the upper left.
• Use USPS address verification tools to prevent delivery delays.

3. Determine Postage

• Weigh your mail to ensure it’s under the maximum weight for its category.
• Check rates on the USPS website or at the post office.
• Apply the right number of stamps or print a postage label.

4. Add Extras if Needed

• For tracking information on letters or flats, purchase Certified Mail or another extra service.
• Add insurance for valuable packages.

5. Send It Off

• Drop it in a USPS mailbox, hand it to a mail carrier, or take it to your local post office.
• Keep your receipt or tracking number if applicable.

💡 Want to skip the manual steps? With LettrLabs’ direct mail automation, you can design, print, and send First Class mail without leaving your desk — and track delivery in real time.

First Class Mail vs Other USPS Options

While first class mail service is a great all-around choice, it’s not the only USPS shipping method. Depending on your package’s weight, budget, and urgency, other services like priority mail, media mail, or usps marketing mail may be better suited.

Quick Comparison Table

Key Takeaways

• Use first class services for everyday personal and business mail that needs a balance of cost effective rates and delivery speed.
• Choose priority mail for heavier items or when speed matters more than price.
• Go with media mail for shipping educational materials at the lowest cost.
• Select usps marketing mail for large-volume, non-time-sensitive promotions.

💡 If you’re deciding between USPS services for a marketing campaign, LettrLabs’ direct mail campaign guide breaks down strategies to maximize ROI no matter which class you choose.

Final Tips for Using First Class Services

If you want to get the most out of first class mail service, keep these best practices in mind:

1. Match the Service to the Item
   • Use letters for documents up to 3.5 ounces, envelopes flats for unfolded materials, and first class package service for lightweight packages.
2. Follow USPS Size and Shape Rules
   • Double-check minimum size, maximum size, and maximum weight to avoid extra fees.
   • Keep your combined length under USPS limits.
3. Leverage Commercial Pricing When Possible
   • If you send in bulk, qualify for commercial prices by presorting and meeting USPS mailing requirements.
4. Plan for Delivery Speed
   • Allow up to 5 business days for arrival, and mail early during holidays or peak seasons.
5. Consider Extra Services for High-Value Items
   • Add tracking information, insurance, or Certified Mail for important shipments.
6. Optimize Packaging
   • Use poly mailers or plain or branded box options to reduce weight without compromising protection.

💡 If you’re ready to put these tips into action, LettrLabs’ direct mail automation can help you send USPS First Class pieces at scale — with built-in compliance, personalization, and analytics.

Why First-Class Mail Postage Remains a Smart Choice

First class mail postage is still one of the most cost effective and reliable USPS options for sending letters, postcards, envelopes flats, and lightweight packages. With delivery in 1–5 business days, automatic forwarding, and access to extra services like tracking and insurance, it’s a flexible choice for both personal and business mailing needs.

Whether you’re mailing a single thank-you note or running a multi-state marketing campaign, first class services give you predictable delivery speed without the high cost of priority mail. And when combined with the right automation tools, it becomes even more powerful — saving you time, reducing errors, and improving ROI.

💡 If you’re ready to make USPS First Class part of a scalable, data-driven marketing strategy, explore LettrLabs direct mail automation and see how we can help you reach the right audience with the right message at the right time.