How do you choose the size for your thank-you note or note card?
The standard thank-you card sizes are:
3.5" x 5"
4.25" x 6"
5" x 7"
Not only will going with a standard size reduce your printing costs, but you'll also have no problem finding envelopes for these. (Think about whether you want your mailing envelopes to be designed and printed or if you need mailing labels. Handwriting your address is a more personalized option, but can get tedious.
The choice of card size depends on how much you tend to write on the inside – you want to have enough space for the length of message that you tend to write, but not to have it look like it's swimming on a blank page. If you leave too much blank space in a card, the recipient can feel short-changed or like you didn't take the average time, care and attention when writing their note.