How many cards are actually worth holding

More cards give you access to more good rates. But the same spending has to be spread across them, each card receives less, and past some point a card can no longer clear its requirement.

There is a simple conservation here. Spending that can count toward requirements is capped by your monthly spending, so the requirements of the cards that do qualify cannot add up past it either. That is where an answer like three cards for a million won a month at three hundred thousand each comes from.

Hold one more beyond that and the reward stays flat while another annual fee appears. So the net curve passes a peak and turns down. A table comparing cards one at a time never shows this point.

The curve screen draws the best net at each count from one card upward, and past the peak it names the card that fell short of its requirement.

Some of what decides the number of cards never reaches the curve. Choosing which card to pull out at the till, statements arriving in several pieces, annual fees landing in scattered months. So this screen neither urges you to add nor to cut, it only lays the numbers out.

A nearly flat curve is common too. If one more card adds a few thousand won a month, whether that is worth the trouble differs from person to person. When it is that close, leaving the wallet alone keeps both it and your head lighter.