Enter your balance, current APR, and a transfer offer to see your savings after the transfer fee, including whether a deferred-interest catch is worth the risk.
Understanding balance transfers
How a balance transfer really works
A balance transfer moves debt from a high-interest card to a new card offering a promotional rate — usually 0% — for a fixed window of 12 to 21 months. During that window, the interest meter is paused (or nearly so), and every dollar you pay goes straight to principal instead of being split with the bank.
That sounds like free money, and sometimes it nearly is. But there are two costs the headline rate hides: the transfer fee you pay up front, and whatever balance is left when the promo ends. Get either wrong and the transfer can quietly cost you more than staying put.
The transfer fee
Almost every balance transfer charges a fee of 3% to 5% of the amount moved. On a $5,000 transfer, that's $150 to $250 added to your new balance on day one. The fee is the price of admission to the 0% window. It's worth paying only if the interest you avoid is larger than the fee — which depends on your old APR, your balance, and how fast you pay it down.
True 0% vs. deferred interest
This is the trap. A true 0% offer simply doesn't charge interest during the promo; anything left over at the end starts accruing at the regular rate from that point forward. A deferred-interest offer is different and far more dangerous: interest is quietly accruing the entire time, and if you don't pay off the entire balance before the promo ends, you're charged all of it retroactively, in one lump.
Deferred interest is common on store cards and some promotional financing. The math is brutal: pay off 99% of the balance and miss the deadline by a day, and you can owe a year or more of interest on the original full amount. This calculator models that retroactive charge when you select "Deferred interest," so you can see the cliff before you walk off it.
A 0% transfer doesn't pay down your debt — it just stops the meter for a while. The payoff comes from what you do during the window, not from the transfer itself.
What this calculator doesn't model
This is a clean, single-balance snapshot. The real world adds wrinkles: new purchases on either card, payments that vary month to month, promo APRs that apply only to transferred balances (not new spending), and the simple human risk of forgetting the deadline. The Pay Down app tracks all of it against your real statements so the answer stays true as your situation changes.
Frequently asked questions
Does a balance transfer actually save money?
Often yes, but not always. A 0% promo APR pauses interest, but you usually pay a transfer fee of 3-5% up front. The transfer saves money only when the interest you avoid during the promo period is larger than the fee — and only if you pay the balance down before the promo ends. This calculator nets all of that out for you.
What is the difference between a true 0% APR and deferred interest?
With a true 0% promo, interest simply doesn't accrue during the promo window — anything left over starts accruing at the regular rate afterward. With deferred interest, interest quietly accrues the whole time and is charged retroactively in one lump if you don't pay the entire balance off before the promo ends. Deferred-interest offers can wipe out your savings; this calculator models that retroactive charge.
How is the transfer fee calculated?
The transfer fee is a percentage of the amount you move — commonly 3% to 5%. On a $5,000 transfer, a 3% fee is $150, added to your new balance up front. The calculator subtracts this fee from your interest savings to show the real net result.
What happens when the promo period ends?
Any balance still owed begins accruing interest at the post-promo APR (usually similar to your old card's rate). If you didn't clear the balance, the transfer only delayed interest rather than eliminating it. The chart shows the post-promo balance trajectory so you can see what's left.
How is this different from the Pay Down app?
This calculator is a one-time snapshot. Your real balance changes every month as you make payments and new purchases, and the promo clock keeps ticking. The Pay Down app connects to your cards, tracks the promo expiry, and recalculates whether the transfer is still paying off as your balance moves.
How long does a balance transfer take?
Most balance transfers take 5 to 10 business days to complete once your new card is approved, though some can take 2 to 3 weeks depending on the issuers involved. Once the transfer posts, interest stops accruing on your old card for that moved balance. Until then, keep paying at least the minimum on your old card. Learn more about the full balance transfer timeline and 0% intro period.
