What paper thickness qualifies for USPS postcard mailing?

USPS accepts postcards that measure between 0.007 and 0.016 inches thick. Both 14pt and 16pt cardstock sit comfortably inside that range, which is why they are the go-to choices for mailers. Ultra-thick stocks are too rigid to qualify and are better saved for cards you hand out in person.

Always check the trimmed thickness of your chosen stock before committing to a large mailing.

In points, that range runs from 7pt, the thinnest postcard the Post Office accepts, to 16pt, the thickest.