According to the official postage website the prices are:
One ounce: 0.83
Two ounces: 1.00

I only put 0.83 on my SASE, but on the outer envelope, I would put 1.00. I send 9X12s folded inside a 6x9 and it weighs exactly one ounce (with letter). Since your envelope is bigger it should weigh more.

Let me know if you need more help. {thumb2}

BossC

I always just put one $1 stamp on it. It seems to work just fine that way.

The Least It Would Cost (Well I send a Letter, and SASE) is 2, 42 cent stamps

9x12 Envelopes require two .42 cent stamps. If you include a peice of thick cardboard, it's best to apply a 3rd one to be on the safe side. {thumb2} Same goes for the SASE as well.

RYAN J.

How much postage does it usually cost to send a 9 x 12 envelope within the US, assuming that the only thing inside is a letter and another 9 x 12 envelope. Since a lot of celebrities send out 8 x 10s I'm assuming this is the best size to send?

Thanks for any input