Cash Back vs Low Interest Credit Card Calculator

Cash Back vs. Low Interest: The Real Math

Choosing between a cash back credit card and a low-interest card depends almost entirely on one question: Do you carry a balance each month?

How Cash Back Cards Work

A cash back card gives you a percentage of every purchase back as a reward. Common rates:

• Flat-rate cards: 1.5% to 2% on all purchases
• Category cards: 3% to 5% on groceries, gas, dining; 1% elsewhere
• Premium cards: up to 6% in specific categories, usually with an annual fee

The catch is the APR (Annual Percentage Rate). Rewards cards typically sit at 19% to 29%, which erases the rewards fast if you carry a balance.

How Low-Interest Cards Work

A low-interest card trades the rewards away for a smaller APR, typically 8% to 18%. It is built for people who carry a balance and want the interest charge to stop hurting.

The Key Formula

Monthly interest cost = Carried Balance × (APR / 12)

Monthly rewards earned = Monthly Spending × Cash Back Rate

Net monthly benefit of cash back card = Rewards Earned − Interest Cost on Cash Back Card

Net monthly benefit of low-interest card = Rewards Earned − Interest Cost on Low-Interest Card

Who Should Choose Each Type?

The Breakeven Balance

There is a specific carried balance at which both cards cost the same. Below that balance, the cash back card wins; above it, the low-interest card wins. This calculator shows you that exact breakeven point.

The Real Cost of Rewards

Take a 2% cash back card at 24% APR. Carrying just $100 of balance costs $2 a month in interest, which is exactly the reward you earned on $100 of spending. You have worked for nothing. Carry $1,000 and the interest is $20 a month, against maybe $40 of rewards on $2,000 of spending, and half your rewards are gone.

That is the whole answer, and it is why the breakeven balance matters more than the reward rate. A credit card is a payment tool. The moment it becomes a financing tool, the rewards stop being the point and the APR is the only number on the page that matters.

One thing this calculator simplifies. Real cards charge interest on the average daily balance, and a card paid in full every month sits in a grace period where new purchases accrue no interest at all. The moment you carry any balance, most issuers suspend that grace period, so new purchases start accruing from the day they post. That makes carrying a balance slightly worse than the arithmetic here suggests, not better.