First class mail weight one stamp

In the United States, the weight limit for First-Class Mail that can be sent with one Forever Stamp is:

• 1 ounce (28.35 grams)

If your letter or package weighs more than 1 ounce, you'll need to add additional postage. The cost of postage increases with the weight of the item, as follows:

• 2 ounces (56.7 grams) to 3.5 ounces (99.2 grams): $0.20 (2 Forever Stamps)
• 3.5 ounces (99.2 grams) to 6.5 ounces (184.8 grams): $0.30 (3 Forever Stamps)
• 6.5 ounces (184.8 grams) to 13 ounces (369.9 grams): $0.40 (4 Forever Stamps)

Keep in mind that these rates are subject to change, so it's always a good idea to check the current rates with the United States Postal Service (USPS) or on their website.