How much can you mail with a first class stamp

In the United States, a First-Class Mail stamp can be used to mail a letter or postcard weighing up to 1 ounce (28 grams). This is the standard weight limit for First-Class Mail letters and postcards.

Here are some specific guidelines:

• Letters: Up to 1 ounce (28 grams) in weight, up to 11.5 inches (29.2 cm) in length, 6.125 inches (15.6 cm) in height, and 0.25 inches (0.64 cm) in thickness.
• Postcards: Up to 1 ounce (28 grams) in weight, up to 4.25 inches (10.8 cm) in length, 6 inches (15.2 cm) in height, and 0.016 inches (0.4 mm) in thickness.

If your letter or postcard weighs more than 1 ounce, you'll need to use additional postage or upgrade to a different mail class, such as Priority Mail.

It's also worth noting that the size and shape of your mailpiece can affect its postage rate. For example, a large envelope or a package may require additional postage, even if it weighs less than 1 ounce.

To check the postage rate for your specific mailpiece, you can use the USPS Postage Price Calculator or consult with a postal worker at your local post office.