Updated Postal Rates for August 2021
Domestic Mailing Price Updates went into effect August 29th, 2021:
The First Class Mail letter (1 oz.) rate for postage purchased at the Post Office will increase to $0.58 (a change of $0.03 from early in the year). That means that Forever Stamps will increase to $0.58, and that the amount you need on an envelope in vintage postage for the forever stamp equivalent (if not using a forever stamp) will still be $0.58 .
Each additional ounce for a First Class Mail letter will cost $0.20, rather than $0.15, a five cent increase from 2020. That means instead of $0.70 for many wedding invitations that weigh 1.1 oz. - 2.0 oz., it will now be $0.83 to mail those invitations, and an additional $0.20 for each additional ounce beyond that.
More detail can be found on the USPS website here.