Your Stamps.com $80 Offer

FREE 5lb Digital Scale

As a new Stamps.com customer you will receive a FREE 5 lb. Digital Scale. The scale is a $50 value and is yours to keep with no additional obligation. Just pay for shipping and handling (typically $9.99 or less).

$25 Postage Offer

As a new Stamps.com customer you will receive $5 in free postage that you can use during your trial period. After you complete your trial period, you are eligible for an additional $20 in postage. We will give you two $10 postage coupons. You can redeem one coupon per month once you complete your trial. If you stay with Stamps.com past the trial period, you will be charged $15.99 a month for the Stamps.com service, you can cancel your services at any time.

FREE Supplies Kit

To help you get started we will ship you a free Supplies Kit that includes free postage labels to use with the service (a $5 value). However, you don't need to wait for the Supplies Kit to arrive in order to print postage. You can immediately take advantage of features such as printing shipping labels on plain paper or printing postage directly on envelopes!

First Class Mail Shape Based Classification Tool

Determine if your mail piece is a Postcard, Letter, Large Envelope, or Package


For First Class Mail, USPS rates are based on the size and thickness of your mail piece. Follow the instructions below to determine the type of First Class Mail you are trying to send.

Step 1:

Measure your mail piece

Step 2:

Determine your mail piece shape

Step 3:

Find the aspect ratio

Step 4:

Print postage and send your mail piece

Using a ruler, measure the length, height, and thickness of your mail piece.

When trying to determine the length, be aware of the following:

  • Letter-sized pieces: Length is the dimension that is parallel to the address.

  • For large envelopes and packages: Length is the longest dimension.

If your mail piece is too thin to measure the thickness, ignore this dimension for now. In addition to dimensions, you will also need to weigh your mail piece.

Step 1:

Measure your mail piece

Step 2:

Determine your mail piece shape

Step 3:

Find the aspect ratio

Step 4:

Print postage and send your mail piece

Using the parameters below, match your mail piece to the shape that fits your mail piece in all dimensions. In order to qualify for a particular shape, your mail piece must meet all qualifications. If your mail piece is too long, wide, thick, or heavy in any single dimension then your mail piece does not qualify for a particular shape. If your mail does not fall into any of these categories (too short or too narrow), it is likely undeliverable as First Class Mail; your mail piece may qualify as a package.

First Class Postcard

Minimum size: 3 1/2 inches tall x 5 inches long and 0.007 inches thick
Maximum size: 4 1/4 inches tall x 6 inches long and 0.016 inches thick

First Class Letter

Minimum size: 3 1/2 inches tall x 5 inches long and 0.007 inches thick
Maximum size: 6 1/8 inches tall x 11 1/2 inches long and 1/4 inches thick
Maximum weight: 3.5 oz.
Aspect ratio - Length divided by height: Ratio must be between 1.3 and 2.5 or the letter will be subject to a non-machinable surcharge. See step 3 for details.

First Class Large Envelope/Flat Mail

Minimum size: 6 1/8 inches tall or 11 1/2 inches long and 0.007 inches thick
Maximum size: 12 inches tall x 15 inches long and 3/4 inches thick
Maximum weight: Up to 13 oz.

First Class Package

Minimum size: 6 inches long, 3 inches high, 1/4 inches thick
Maximum size: 34 inches long, or 17 inches high, or 17 inches thick
Maximum weight: 13 oz. (4 lbs. for international)
Dimensions or weights smaller than the minimum or larger than the maximum may qualify as a package but be subject to non-machinable surcharges.


Step 1:

Measure your mail piece

Step 2:

Determine your mail piece shape

Step 3:

Find the aspect ratio

Step 4:

Print postage and send your mail piece

If you believe your mail piece may qualify as a letter, you will need to determine the aspect ratio by dividing the length by the height. In the example of the letter below, the aspect ratio would be (9.5 inches by 4.125 inches) resulting in an aspect ratio of 2.3. Aspect ratios less than 1.3 or greater than 2.5 are subject to a non-machinable surcharge.

Step 1:

Measure your mail piece

Step 2:

Determine your mail piece shape

Step 3:

Find the aspect ratio

Step 4:

Print postage and send your mail piece

Once you have determined your mail, it's easy to print postage for your First Class mail piece with Stamps.com. With Stamps.com, you can print postage for any mail class without a trip to the Post Office. Not a Stamps.com customer? Click here for a no-risk 4-week trial and send your mail today!

For more help with First Class Mail classifications, visit the Stamps.com Store to obtain a shape-based template to help with your mailings!

Try Stamps.com for 4 Weeks!

Every new customer account starts with:

  • Free 5 lb. Digital Scale, connects via USB
  • 4-week trial
  • $5 in free postage to use in trial period
  • Free Supplies Kit including postage labels
  • Additional $10 postage coupons to use after trial

*pay only s&h fee

Get Started

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