Rewards vs Interest: The Math Showing Why a Carried Balance Erases Every Rewards Program
A rewards card pays you a percent or two on spending; a carried balance charges you more than 20% on the balance and usually on new purchases too. Here is the math, including the trailing interest that surprises people after they pay off.
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📐 Figures verified Sep 28, 2026 against the Federal Reserve's G.19 card rates (May 2026) and Regulation Z's rules on statement timing (12 CFR 1026.5), payment allocation (1026.53) and finance-charge limits (1026.54), plus the CFPB's card agreement database. Grace-period details vary by card agreement. How we check numbers →
Rewards pay about 1% to 2% a year on spending, while a carried balance costs the average 22.15% on the balance, and carrying one usually cancels your grace period, so new purchases charge interest too. In our example, $360 of rewards meets about $831 of interest. Pay the balance off first; rewards only work when you pay in full.
Numbers That Matter
| Figure | Amount | Source | Verified |
|---|---|---|---|
| Average card APR, accounts charged interest | 22.15% (May 2026) | Federal Reserve G.19 | Sep 28, 2026 |
| Time to pay in full and keep the grace period | At least 21 days between statement and due date | Regulation Z, 12 CFR 1026.5 | Sep 28, 2026 |
| Interest on balances from earlier cycles | No "double-cycle" billing; no interest on amounts repaid within a grace period | Regulation Z, 12 CFR 1026.54 | Sep 28, 2026 |
| Payments above the minimum | Must go to the highest-rate balance first | Regulation Z, 12 CFR 1026.53 | Sep 28, 2026 |
| Your grace-period terms | Spelled out in your card agreement | CFPB | Sep 28, 2026 |
How the Grace Period Works, and How You Lose It
If you pay your full statement balance by the due date, most cards charge no interest on purchases: that's the grace period. Carry any balance past the due date and most issuers remove it, so new purchases start charging interest from the day you make them. You usually get it back only after paying in full for one or two billing cycles, depending on your agreement.
Trailing Interest: The Surprise After You Pay Off
When you finally pay the statement balance, interest has still been building from the statement date until your payment posts. It shows up on the next statement as residual or trailing interest. Pay that small amount too, or it starts the cycle again.
Payment Allocation
If you have balances at different rates, such as a promotional transfer and regular purchases, the law requires payments above the minimum to go to the highest-rate balance first. The minimum itself can go to the lowest-rate balance, so paying only the minimum lets expensive balances linger.
Worked Example: 2% Back, 22% Interest
- Paying in full every month: rewards of $360 a year, no interest.
- Carrying $3,000: without a grace period, interest runs on about $3,750 on average, costing about $831 a year at 22.15%. Net: a loss of $471.
- The fix: moving the $3,000 to a 0% transfer with a 4% fee costs $120 instead of about $664 a year of interest on the balance alone; paying it off restores the rewards.
- Trailing interest: on payoff day, about $41 of interest from the last half-month can still post. Pay it so the grace period comes back.
Simplified: interest on an average daily balance at the G.19 average rate; your card's terms and timing will differ.
Decision Rules
If this, then that
- If you carry any balance → stop optimizing rewards and put every spare dollar toward the balance.
- If you can't pay it off within a few months → compare a 0% balance transfer or a lower-rate loan.
- If you just paid off a balance → pay the next statement in full too, including trailing interest.
- If you keep carrying balances → use debit or cash for daily spending until the card is clear.
- If you pay in full every month → then choose rewards that fit your spending.
Mistakes to avoid
- Counting rewards while ignoring interest.
- Making new purchases on a card that's lost its grace period.
- Assuming a statement paid in full means no more interest.
- Paying only the minimum on a card with several rates.
- Choosing a card for rewards when a low rate would save more.
Related: how to choose a credit card starts with the balance question; is the annual fee worth it? covers fee break-evens; how to pay off credit card debt lays out payoff plans; and credit utilization explains how balances affect your score.