Not sure because I've never used the wallet. But there are three dedicated credit card slots, aside from the ID window slot and the coin zipper area. So maybe 4-8 cards, in addition to your ID?
I don't have a ruler handy, but added two more pics w/ a business card for reference. The card is 3.5" x 2" - in the last picture the card is all the way at the bottom of slot so you can see how deep it is. Hope that helps!