The "No. 10" envelope (9.5" x 4.125") is the most common choice.
For regular letters (First-Class Mail), you generally have to buy your own envelopes. usps buy envelopes
The USPS provides shipping supplies if you use their expedited services. You can order these on the official USPS Store. The "No
To qualify for standard letter rates (starting at for a Forever stamp), your envelope must meet these USPS requirements : Shape: Must be rectangular. Max Size: 11.5" long x 6.125" high. Thickness: No more than 1/4" thick. usps buy envelopes
Most locations sell individual or small packs of plain and padded envelopes.
You can get envelopes from the USPS either for free (for specific premium services) or by purchasing them for standard mail. 📦 Get Free Envelopes