0% balance transfer

The math at a glance: a balance transfer rolls existing card debt onto a new card with a promotional 0% (sometimes 1-3%) APR for 12-21 months. You pay a transfer fee of 3-5% of the balance upfront. If you fully pay off the balance + fee within the promo window, total cost is just the fee. If not, the remaining balance starts accruing at the fallback APR (typically 22-29%) — and depending on terms, may also trigger retroactive interest.

The required-monthly numberis the headline above. It's simply: (balance + fee) ÷ promo months. If your honest budget can sustain that number every month for the full promo window, balance transfers are a real win. If not, you're likely better off with debt consolidation, avalanche payoff on existing cards, or some combination.

The deferred-interest trap:two ways "0% intro APR" gets applied:

Standard waived-interest (most major BT offers from Chase, Discover, Citi, AmEx): no interest charged during the promo. If anything remains at promo-end, the fallback APR starts accruing on the remaining balance only, from that day forward. Bad but not catastrophic.

Deferred-interest(common on store cards — Best Buy, Home Depot, Synchrony-issued, Wayfair, etc.): the interest at the fallback APR IS accruing every month during the promo, the card just doesn't charge it. If you pay off in time, the accrued interest disappears. If you miss the window by even $1, the entire accrued amount getsretroactivelyadded to your balance from day 1. On $8k at 26.99% over 18 months, that's ~$3,300 in surprise interest. The 0% APR was never really 0% — it was conditional.

Read the cardmember agreement carefully.Look for the phrase "deferred interest" or "interest charged if balance not paid in full by [date]" — that's the trap. Standard BT language uses "no interest during the introductory period" without back-charge clauses. The toggle in the form lets you model both.

Effective APR including the fee:even at 0% promo APR, the transfer fee acts like an upfront interest charge. On $8k at 3% fee paid off in 18 months, effective APR is about 3.2%. Compare that to the rate you'd pay on a personal loan consolidation (often 8-15%) and balance transfer wins handily — provided you clear the window.

What we deliberately don't model:new charges made on the BT card during the promo (often subject to a separate regular APR that compounds in confusing ways); intro APR rate-jacks if you miss a payment (some BT terms terminate the promo on first late payment); minimum-payment requirements during the promo (typically 2% of balance or $25, but if your planned payment is below this you'll trigger late fees and possibly promo termination); credit-utilization impact on your score (transferring debt to a card with high utilization briefly dings your score until it pays down).

When BT clearly wins:high-confidence you can pay off within the window + standard-terms card + balance large enough that 3-5% fee << alternative APR cost. When BT is dangerous: deferred-interest terms + uncertain payoff timeline. When BT is a wash: short window + small balance + uncertain budget. Then debt consolidation or avalanche are simpler.