How balance transfer cards work, with the fee math

A balance transfer card lets you move debt from a high-interest card onto a new card that charges a low or 0% intro APR for a set number of months. You usually pay a one-time balance transfer fee to do it, and the deal only works if you pay the balance off, or close to it, before the intro period ends.

Done well, it turns interest you would have paid into principal you actually pay down. Done badly, it just moves the debt and adds a fee.

How a balance transfer works

1. You apply for a card that offers an intro APR on balance transfers. Experian suggests these cards generally suit people with a credit score of at least 670 who have high-interest balances they can clear within the promo period.
2. You request the transfer, giving the account details of the card you want to pay off. You usually can't move a balance between two cards from the same issuer.
3. The new issuer pays off the old balance. The amount you moved, plus the transfer fee, appears on your new card.
4. You pay the new card down during the intro period. Keep paying the old card until you see the transfer has posted.

Your new credit limit caps what you can move. Experian notes the limit may mean you can transfer only part of an existing balance. Many offers also require you to make the transfer within a set window, such as 60 days of account opening, to get the intro rate.

The three numbers that matter

These vary by card and change often. Read the actual terms before you apply.

The fee math

The fee is real money, so check that the interest you avoid is bigger than the fee you pay. Here is an example with round numbers, not any real card's terms.

Say you owe $6,000 on a card charging 24% APR. You can afford about $412 a month.

Option 1: stay put. At $412 a month, it takes about 18 months to clear the debt, and you pay roughly $1,160 in interest.

Option 2: transfer to a card with a 15-month 0% intro APR and a 3% fee.

• Fee: $6,000 × 3% = $180. Your new balance is $6,180.
• Payment to clear it in time: $6,180 ÷ 15 = $412 a month.
• Interest: $0, if every payment is on time and the balance hits zero by month 15.

The transfer saves about $980 in this example ($1,160 of interest minus the $180 fee), and you finish three months sooner. With a 5% fee, the fee is $300 and the payment rises to $420 a month. It is still a large saving.

The math gets worse when the debt is small or you can clear it quickly anyway. CNBC Select gives an example of a $2,000 balance at 21.99% APR paid off in two months: you would pay about $36.65 in interest, while a 3% transfer fee would cost about $60. In that case the transfer costs more than it saves.

Build the payment plan before you apply

The minimum payment on a balance transfer card is designed to keep the account current, not to clear the balance by the deadline. Make your own plan:

1. Add the fee to the amount you plan to transfer.
2. Divide by the number of months in the intro period, minus one month as a safety buffer.
3. Set autopay for that amount, not the minimum.
4. Put the intro end date in your calendar, with a reminder two months earlier.

Using the example above: $6,180 ÷ 14 months is about $442 a month. That buffer gives you room for one tight month.

What happens when the intro period ends

Any balance still on the card starts accruing interest at the card's standard APR. Federal rules under Regulation Z let an issuer raise a rate when a promotional period of six months or longer expires, as long as it disclosed the length of the period and the rate that will follow in advance.

Back to the example. If you paid only $200 a month instead of $412, you would have paid $3,000 after 15 months. That leaves $3,180 on the card, now at the standard APR. You saved some interest, but you are still in debt at a high rate.

This is a card with a regular 0% intro APR, not a deferred interest plan, so the standard APR applies only to what is left, not back to the transfer date. Store financing often works differently. Our balance transfer and 0% APR section has a separate guide on 0% intro APR vs deferred interest.

Traps that cost people the deal

Paying late

Experian warns that a late payment can cost you the 0% intro APR. Under Regulation Z, an issuer can raise your rate if it does not receive your minimum payment within 60 days after the due date. It must then lower it again after six on-time minimum payments in a row, but the damage is done in the meantime.

Spending on the same card

This one surprises people. A CFPB bulletin warns that if you accept a promotional balance transfer offer and keep making purchases on that card, you lose the grace period on new purchases unless you pay the entire statement balance, including the transferred amount. In plain terms, your new purchases start accruing interest right away. Use a different card for spending.

How payments are applied

Under Regulation Z, the issuer must apply any amount you pay above the minimum to the balance with the highest APR first. The issuer can decide where the minimum itself goes. If you have both a 0% transfer and full-rate purchases on the card, the purchases get paid first and the transfer waits. That is one more reason to keep new spending off the card.

Running the old card back up

Moving the debt frees up your old card's limit. If you spend it again, you end up with two balances instead of one.

Credit score effects

Applying for a new card means a hard inquiry. Experian says a hard inquiry generally affects your credit scores for up to a year and can drop them by up to five points, and it stays on your report for two years. A new account also lowers the average age of your accounts. As you pay the balance down, falling utilization usually helps more than these small dips hurt.

Who should not use a balance transfer card

• People who cannot afford a payment close to balance ÷ months. You would pay a fee and still face the standard APR.
• People whose debt is small enough to clear in a couple of months anyway.
• Anyone still spending more than they earn. Fix the cash flow first, or the old card fills back up.

If a rewards card is what you are really after, see our cash back cards guide. Rewards are not worth much while interest is running.

Bottom line

A balance transfer card swaps ongoing interest for a one-time fee, and the swap pays off when you clear the balance inside the intro period. Before you apply, add the fee to the balance, divide by the months, and check you can pay that amount every month. Pay on time, keep new spending on another card, and treat the intro end date as a hard deadline.