For a one touch, 100pt.
For a toploader, 120pt-130pt.
That said the one DP Guernsey card I have was too long to fit in a one touch, and there's not much you can do about that.
A good rule is 1 standard card = 20pt.
Stack some commons against the Guernsey card, and see how many it takes to match its thickness. Multiply that total by 20 and you get a good idea of how thick it is.