Postage on A7 Envelopes

I don't know why I am stressing over this.
I have to make a point to go to the post office to ask about the postage on A7 (5 1/4″ x 7 1/4″) but, was wondering if anyone could help me. I'm mailing out my "Save the Date" at the end of the month, I've already weighted everything myself (11 g). Is it only one postage or do I need a 2nd one to ship them within Canada. Once again I do not know why this causing me stress, lol.