Cost to mail???

[hoptownracer1]

Does anyone know how much it cost to mail a size A9 card/envelope? I looked on the USPS site, but I am a little confused. Is A9 considered a regular shape? I think it says it cost .60, but wanted to double check. If an envelope has a size number (like A9), is that considered a regular envelope with no problems with mailing regular .60 postage?
Thank you in advance for any feedback!

[Arlene_C]

standard letter size is from 3 1/2" x 5" up to 6 1/8" x 11 1/2" and 1/4" thick. These require only 1 stamp for weight up to 1 ounce.
201 Quick Service Guide | Postal Explorer (usps.com)

[hoptownracer1]

Thank you so much Arlene!!! That's kind of how I was understanding it, but I am sleep deprived, so I didn't trust my brain! lol...

[fionna51]

If any dimension exceeds the measurements Arlene mentioned above, then it needs extra postage.

And square envelopes require extra postage regardless of their size.

[hoptownracer1]

Thank you Diane!