What is First Class Mail? – All You Need To Know About It!

When you need to send a parcel or letter through the mail, how do you decide what service is the best? And what service will get the package delivered in the best time frame?

Sending mail or packages should be an easy task to accomplish but, with all the options and delays out there today, what is the best option, and what are the restrictions that come with those options.

Today, I will explore one of the best mailing options and what you need to know when using it.

What is First Class mail?

First Class Mail is a mailing service that you can use to send packages through the postal service for delivery within a nominated number of business days. The delivery days get determined from the date reflected on the postmark stamp. Well, there are plenty of sources to find and buy stamps online in case you don’t want to visit your local stores.

The benefits of sending a parcel or letter via Frist Class service are:

  • Delivery usually takes place within 1-3 business days
  • One of the best-priced options
  • The post will have insurance to a degree for loss and damages
  • Packages are eligible for services such as Certified Mail
  • One price for items up to three and a half ounces
  • Pricing for this service gets based on the shape and weight of the shipment

First Class Mail Weight and Shape Restrictions

The shape and size of parcels have certain restrictions when being processed through the postal service.

The maximum weight allowed is three and a half ounces for letters and 13 ounces for larger envelopes and packages.

All postcards and envelopes sent through this infrastructure must be rectangular or additional charges will be levied.

Any envelope or parcel sent as a First-Class item that is lumpy, has buttons or strings attached will be classified as nonmachinable and attract levies.

These levies apply even when the package weighs less than one ounce. Well, yeah, it’s when you use USPS to deliver your packages.

Different kinds of First-Class mail.

  • Letters

Letters may seem like a regular item sent through the postal service, and they are, but there are some rules that you need to abide by.

Letter guidelines

  • Each letter on its own can only weigh one ounce.
  • Each additional ounce requires another stamp.
  • The maximum size of a letter is ½” x 1/8” x 1/7” thick.
  • If a letter is biggerer than this, then it is classified as a flat or large envelope.
  • The maximum weight of letters is three and a half ounces.

Because letters get sent through machines, some rules by USPS apply, and if the letter is outside of these regulations, they can no longer get classified as letters.

Large Envelopes or Flats

  • The maximum size is 15” x 12” x ¾”.
  • The maximum weight is 13 ounces.
  • All large envelopes must be rectangular.

Packages or Parcels

  • Packages going through the system as First-Class Mail can only weigh up to 13 ounces.
  • Each package requires a First-Class package stamp.

Nonmachinable Criteria for Priority Mail:

A nonmachinable item does not fit the automation standards for the machines used in the postal system. There are three types of nonmachinable letters.

  • When the envelope has a window in it
  • Any pieces with any attachments on them
  • A letter that weighs more than 3.5 ounces
  • Additional reasons that parcels cannot go through the machines are:
  • The package is wrapped in anything other than paper. Materials like plastic, poly wrap, and polybags, are all materials that cannot go through the machines.
  • Any closure devices like buttons, strings, or clasps on the outside make the parcel incompatible with the machines.
  • If the parcel has any pens, keys, coins, pencils, or other items that make them an uneven shape, they cannot go through this system.
  • Pieces that are more than 4 ¼” high and 6” long cannot go onto the machines.

Some helpful tips for First Class mail

  • Square greeting cards are applicable for First-Class mail services
  • If the mailpiece has the following measurements: 11 ½” or six and 1/8″ and ¼” thick with a weight of more than 3.5 ounces, it cannot be sent as First-Class Mail.
  • There is a nonmachinable surcharge that applies to First-Class mail. This charge does not apply to large envelopes, postcards, and letters.
  • Whenever cards or letters in First-Class mail exceed the minimum sizes in length, height, and weight, they get classified as flats or large envelopes.
  • Any mail piece sent that is larger than ¾” thick is classified as a parcel.
  • Padded bags get seen as large envelopes or flats.

The First Class Mail Process

Mail sorting and delivery may seem like a standard process, but there are many steps involved. Let’s look at the process from start to finish.

  1. You will put the letter into the envelope and address it to its intended destination.
  2. Place a stamp on the top right-hand corner
  3. Drop the letter off into your nearest mailbox
  4. The mailman comes around and collects all the mail
  5. Mail gets delivered to a Sectional Facility
  6. Along with all the other mail collected, your letter gets sorted
  7. Sorted mail gets transported to LAX for a flight to its destination Sectional Facility
  8. Letters get sorted again
  9. A mail carrier traveling along the intended route gets handed the mail
  10. The letter gets delivered to the recipient’s mailbox

The above process can take anywhere from 1 – 3 business days to complete.

Delivery can be affected by delays, and this will interrupt the standard delivery expectations.

First Class Mail Delivery Delays

Yeah, in some case, packages might get delayed but you can always pick your package directly from USPS in case of delays.

Some common reasons for your First-Class mail to be delayed are:

  • Adverse Weather

When it is deemed unsafe for the carrier to go out in bad weather, the delivery of your parcel or letter gets affected.

Severe weather and natural disasters are the main culprits causing these delays.

  • Incorrect Address

If an address has been made out incorrectly on the package, it will not be delivered, and you will suffer potentially huge delays.

Even a small error such as a digit missing on the postal code can cause your mail to experience such delays.

  • Sorting Facility Backlog

Peak seasons such as Christmas, the facilities processing your mail experience massive influxes of postage.

This influx ranges from parcels to envelopes and postcards, causing delays at the mailing facilities.

Either way, peak times put pressure on the normal flow of things and can cause you some delays.

  • Federal Holidays

Postal services do not operate on holidays. If you need your item delivered before a federal holiday, it is wise to post it with a few days extra in mind to ensure timely delivery.

  • First Class Time Map

Since you cannot track your First-Class mail, the USPS has what they call a “Time Map”. This map outlines the various destinations delivered to and the time that it takes to get there. Yeah, they usually don’t be late in deliveries, but in some cases and due to some uncertainty there might be a bit of delay too.

Package TypeService LevelWeight LimitDimensions
PackageFirst-Class Package15.9 oz22" x 18" x 15"
PackageParcel Select Ground70 lbsLength + Girth < 130"

First Class shipping and Standard shipping do not work on the same timelines and, the map aids you in figuring out which is which.


First Class Mail is a slightly more expensive option for sending small parcels and envelopes across the United States.

The service offering of the USPS makes this the leading service when it comes to critical mail. Your parcels are insured up to a specified value and will get to you within three days.

For a fast and efficient option, First Class Mail has it all.


1. Does the USPS deliver on weekends?

The postal service delivery days are Monday to Saturday. Deliveries do not take place on a Sunday or any Federal Holidays.

2. Can I change the destination of my parcel?

Yes, you can ask that your parcel gets delivered to a different destination. This is common for receivers who have gone away and need to change the delivery address.

You need to make sure that your parcel has not already gone to its final delivery destination to do this.

3. Can I go collect my parcel?

Yes, you can intercept your parcel. Intercepting your post for collection is only applicable if it has not already passed the point you would like to collect it.

You will also need to bring identification with you to prove that you are the intended recipient/

4. What are the standard mail sizes?

Package TypeService LevelWeight LimitDimensions
PackageFirst-Class Package15.9 oz22″ x 18″ x 15″
PackageParcel Select Ground70 lbsLength + Girth < 130″
PackagePriority Mail70 lbsLength + Girth < 108″
PackagePriority Mail Express70 lbsLength + Girth < 108″
Flat Rate Small BoxPriority Mail70 lbs8-5/8″ x 5-3/8″ x 1-5/8″
Flat Rate Medium Box Priority Mail70 lbs
  • Box 1= 11-1/4″ x 8-3/4″ x 6″

  • Box 2= 12″ x 3-1/2″ x 14-1/8″
Flat Rate Large Box Priority Mail70 lbs12″ x 12″ x 5-1/2″
Regional Rate Box APriority Mail15 lbs
  • 10-15/16″ x 2-3/8″ x 12-13/16″

  • 10″ x 7″ x 4-3/4″
Regional Rate Box BPriority Mail20 lbs
  • 14-3/8″ x 2-7/8″ x 15-7/8″

  • 12″ x 10-1/4″ x 5″

Envelope Type

Envelope TypeService LevelWeight LimitDimensions
LetterFirst Class3.5 oz11-1/2″ x 1/4″ x 6-1/8″
Flat Rate EnvelopePriority Mail70 lbs12-1/2″ x 9-1/2″
Flat Rate EnvelopePriority Mail Express70 lbs12-1/2″ x 9-1/2″
Flat Rate Padded EnvelopePriority Mail70 lbs12.5″ x 9.5″
Flat Rate Padded EnvelopePriority Mail Express70 lbs12.5″ x 9.5″
Flat Rate Legal EnvelopePriority Mail70 lbs15″ x 9-1/2″
Flat Rate Legal EnvelopePriority Mail Express70 lbs15″ x 9-1/2″

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