Which of my cards should I use?
Tick the cards in your wallet, then pick a store or a kind of spending. They are ranked by what each earns on that purchase, in dollars per $100 — the same answer the extension gives at a checkout, from the same catalogue of 69 cards.
This calculator needs JavaScript. The same rankings, for the whole catalogue, are on the category guides.
Nothing you choose here leaves this page: your picks live in the address bar after the #, which a browser never sends to a server — so a link to this page carries them, and nothing else does. How the numbers are worked out.
Do this at every checkout, automatically.
Cardful remembers your cards and ranks them at the store you are on.