Which credit card should I use for this purchase?
Last reviewed
Use the card that pays the most for that specific category, has not already spent through its bonus cap, and does not charge you interest you cannot avoid. If you are carrying a balance, the answer is almost always the cheapest card to borrow on, not the one with the best rewards - interest at a typical APR outruns a few percent of cashback.
The four things that decide the answer
Picking a card for a purchase is not a matter of taste. Four facts decide it, and three of them are printed on the issuer's own product page.
- The earn rate for that category. A card that pays 3% on groceries and 1% elsewhere is the right card in a supermarket and the wrong card at a petrol pump.
- The cap on that rate. Bonus rates usually stop at a monthly or quarterly spend cap. Once the cap is spent, the card earns its base rate and the ranking flips.
- The annual fee, in the cadence the issuer prints it. A fee stated monthly and a fee stated yearly are not comparable until one is converted, and the conversion is arithmetic you did, not a figure the issuer published.
- Whether you carry a balance. Rewards are a percentage of what you spend; interest is a percentage of what you owe, charged daily. Carrying a balance usually erases the reward before you redeem it.
Rewards only win while you are not paying interest
A card paying 2% back on a $1,000 purchase earns $20. The same $1,000 left on a card at a 24.99% APR costs roughly $20 in interest in the first month alone, and keeps costing it every month it stays. That is the whole reason a rewards ranking has to know whether you are paying your statement balance in full.
This is not an argument against rewards. It is an argument for answering the boring question first: am I clearing the statement balance? If yes, optimise the earn rate. If no, optimise the borrowing cost and treat the rewards as rounding.
Why the answer changes during the month
Most "best card" advice is written once and left standing. Real answers move. A quarterly bonus cap fills up halfway through March and the card that was winning stops winning. A fee changes. A promotional rate ends. A card you were about to use is the one holding the balance you are trying to clear.
Anything that answers this question usefully therefore has to track your own spending against the caps, not just hold a table of rates.
How to judge any "which card" tool
Several apps answer this question. These are the tests worth applying to any of them, including this one - each answer below is what CardLab does, which you can check on the pages linked from it.
Can it show you where the rate came from?
A rate with no source is a rate you cannot check. Every earn rate and annual fee CardLab publishes stores the issuer page it was read from, the exact sentence on that page, and the date it was read: 1,098 of 1,098 claims in the shipped catalog carry all three.
Does it know your caps, or just the headline rate?
A bonus rate that has hit its cap is not the rate you will be paid. CardLab tracks spend against each card's cap and drops a card down the ranking when the cap is spent, then says that is why.
Does it get paid by the cards it recommends?
Referral commission and ranking cannot both be honest. CardLab takes no commission from any issuer; no card is ranked or featured because of a payment.
Does it need your bank login?
CardLab never asks for one. You enter the cards you hold, or import a statement that is read on the phone, and nothing is sent to a server to be linked.
Does it work where you live?
The card ranking is offered only in markets with a verified catalog - currently 17: United States, Canada, United Arab Emirates, United Kingdom, Japan, Australia, France, Indonesia, Saudi Arabia, the Philippines, Singapore, Brazil, Italy, Mexico, Germany, Spain, Hong Kong. In every other country preset the tracker and simulators still work, because they compute from the terms you enter.
Does it show its working?
A winner with no arithmetic is a guess you cannot audit. CardLab shows the comparison behind the ranking, including the point at which the order would change.
See which cards are covered where
The catalog currently holds 372 cards from 73 issuers, each rate carrying the sentence and date it was read from.
Common questions
Which credit card should I use for groceries?
Use the card with the highest grocery earn rate that still has room under its bonus cap, provided you clear the statement balance in full. If a card pays 3% on groceries up to a quarterly cap and you have already spent that cap, it now pays its base rate, and a flat 2% card is the better choice for the rest of the quarter.
Should I use a rewards card if I carry a balance?
Usually no. Interest is charged on what you owe, every day, at a rate far above any cashback percentage. On a balance carried at a typical APR, the interest in a single month can exceed a year of rewards on the same spending. Clear the balance first, then optimise for rewards.
How do I compare two cards with different annual fees?
Convert both fees to the same period, then work out how much category spending it takes for the extra earn rate to cover the extra fee. Below that break-even spend the cheaper card wins. Note the cadence the issuer actually prints: a fee published monthly is not an annual figure until you multiply it yourself.
Does CardLab tell me which card to use?
Yes. Best Card ranks the cards you track for a chosen purchase or purpose, using rates verified from issuer pages, and shows the arithmetic behind the order rather than just a winner. It is cap-aware, and it is offered only in markets where CardLab has a verified catalog.
Do I have to connect my bank for this?
Not with CardLab. You add the cards you hold yourself, or hand it a statement PDF or screenshot that is read on the device. There is no bank login, no card number and no CVV, and nothing about your cards is sent to a server.