
First class mail weight is calculated based on the weight of the mailpiece, with a maximum weight of 13 ounces for retail and commercial mail.
The US Postal Service uses a standardized system to determine the weight of mailpieces, taking into account the weight of the mailpiece itself, as well as any additional packaging materials.
For retail mail, the weight is calculated by adding the weight of the mailpiece and any additional packaging materials, such as envelopes or boxes.
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Weight and Cost
First Class Mail has a weight limit of 13 ounces for retail pricing, but commercial pricing allows for a maximum weight of 15.99 ounces.
Exceeding the weight limit can result in additional charges or even returned mail, so it's essential to weigh your mail carefully before sending.
The cost of sending First Class Mail varies depending on the weight of the mail. For example, a letter weighing 1 ounce costs $0.60, while a letter weighing 2 ounces costs $0.84.
Here's a breakdown of the cost of sending First Class Mail based on weight:
If your letter weighs more than 3.5 ounces, you'll need to use USPS shipping services like First Class Package or Priority Mail.
It's also worth noting that Forever Stamps only cover the cost of one ounce of mail, so if your letter weighs more than 1 ounce, you'll need to add additional ounce stamps to the cost.
For example, a letter weighing 2 ounces would require one Forever Stamp and one additional ounce stamp, which would cost a total of $0.87.
USPS Requirements
Letters that weigh more than 1 ounce require additional ounce stamps on top of your first Forever Stamp.
You need one Forever stamp and one additional ounce stamp for a 2-ounce letter, and one Forever stamp and two additional ounce stamps for a 3-ounce letter.
If your letter weighs 3.5 ounces, you'll need a total of four stamps, one Forever and three additional ounce stamps.
First Class letters can only weigh up to 3.5 ounces per mail piece, so if you need to send heavier items, consider breaking them up into separate envelopes or shipping them together using a single Priority Mail Flat Rate Envelope.
The maximum weight for a First Class letter is 3.5 ounces, and you can use the postage rate chart below to see the cost for different weights.
Commercial Mail
Commercial Mail is a type of mail service that's often used for business purposes, such as sending invoices and marketing materials. It's typically more expensive than regular mail.
The cost of commercial mail varies depending on the weight and size of the package, as well as the distance it needs to travel. For example, a 1-ounce letter sent via commercial mail might cost around $1.50.
Commercial mail services often offer tracking and insurance options to ensure that packages arrive safely and on time.
Commercial Letters and Postcards Automation
Commercial letters and postcards can be sent via automation, which streamlines the process and saves time.
The maximum weight for commercial letters and postcards varies depending on the automation type. For five-digit automation, the maximum weight is 3.5 ounces.
You can send commercial letters and postcards with a maximum weight of 1 ounce for $0.455 using five-digit automation. The cost remains the same for 2 and 3 ounce letters, but increases for 3.5 ounce letters.
The cost for commercial letters and postcards sent via automation is as follows:
Postcards can be sent via automation for a lower cost than letters. The cost for postcards is $0.330 using five-digit automation.
Commercial Parcels
Commercial parcels have their own set of postage rates, which can vary depending on the delivery zone and package weight.
The USPS charges for commercial parcels based on the delivery zone and package weight, with prices ranging from $3.37 to $6.28 for a First-Class Commercial parcel.
If you're shipping irregular-shaped parcels, be prepared to pay an extra $0.25 on top of the regular postage rate.
To determine the correct postage for your First-Class Commercial parcels, check out this handy table:
Retail and International Mail

For retail mail, First-Class postage rates vary depending on the weight of the package and the zone of delivery. You can check the table below to find the postage rate for your parcel.
If your parcel exceeds 22 inches in length, you'll need to add another $4.00 to the postage, and if it exceeds 30 inches, you'll need to add another $15. Keep in mind that packages over two cubic feet also add $15 to the First-Class postage.
For Retail Parcels
When sending retail parcels via First Class Postage, it's essential to consider the weight and dimensions of your package. The postage rate can vary depending on the zone of delivery and the weight of the package.
For packages weighing 1-4 ounces, the postage rate starts at $4.50 for zones 1-2, increasing by $0.10 for each subsequent zone.
The table below shows the postage rates for First-Class Retail parcels by weight and zone:
If your parcel exceeds 22 inches in length, you'll need to add an extra $4.00 to the postage rate. And if it exceeds 30 inches, you'll need to add another $15.
International Mail
International mail can be a bit of a challenge, especially when it comes to figuring out the postage costs. For a retail letter weighing 1 oz, the cost is around $1.40 to send to international addresses.
The postage rates can vary depending on the country and the weight of the letter. In fact, the rates can go as high as $5.04 for retail letters and $14.68 for large retail envelopes weighing up to 15.999 oz.
USPS categorizes countries into different groups, and the postage differs for each group. However, commercial pricing can often get you a better rate than retail pricing.
Here's a rough idea of what you can expect to pay for international mail:
Keep in mind that these rates are subject to change and might not reflect the current rates. It's always a good idea to check with USPS for the most up-to-date information.
Physical Characteristics
Your First-Class Mail letters can weigh a maximum of 3.5 oz, and for envelopes and parcels, they can go up to 13 oz.
Letters or postcards must be rectangular to avoid additional charges.
Using irregular or nonmachinable envelopes can increase First Class postage rates for your mailers.
Frequently Asked Questions
How heavy can a first-class envelope be with one stamp?
A first-class envelope can weigh up to 1 ounce with a single stamp, but additional postage is required for heavier letters. Exceeding the 1-ounce limit may incur extra postage fees.
How many stamps do I need for 3 oz first-class?
For standard-sized letters weighing 3 oz or less, one first-class stamp is required.
Sources
- https://www.onlinestamp.net/understanding-weight-limits-for-first-class-mail/
- https://www.shippingschool.com/how-heavy-can-a-letter-be-for-a-first-class-stamp/
- https://www.postalytics.com/blog/first-class-postage-everything-you-need-to-know/
- https://goshippo.com/shipping/usps-first-class-package-service
- https://www.postgrid.com/how-much-is-first-class-postage/
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