Balance transfer breakeven calculator

Key takeaway: A balance transfer fee is a purchase — at 3%, you're paying $3 per $100 moved to buy months of 0% interest. Whether that purchase pays for itself depends entirely on how much interest your old card would have charged in the meantime, and this calculator finds the exact month it does (or tells you it never will).

You're carrying a balance at a regular APR — the U.S. average is currently 24.35% — and an offer in hand promises 0% for 12, 15, or 18 months in exchange for a one-time fee. This calculator exists for that moment: before you apply, it prices the trade. If you've already ruled out transferring and just want a payoff date, the standard payoff calculator is the simpler tool.

Pricing the window: the formula in plain English

The decision reduces to one comparison, run month by month. Path one: your balance amortizes at your current APR with your monthly payment. Path two: your balance plus the fee (fee percent × balance, capitalized on day one) pays down at the promo APR until the window closes, then at the post-promo APR on whatever's left. The transfer has paid for itself at the first month where path two's running total of payments falls below path one's — and stays there.

Take the defaults: $6,200 at 22.9% APR, $200 a month, a 3% fee, 0% for 15 months, 24.9% after. The fee is $186, so the transferred balance starts at $6,386 — you owe more the day after transferring than the day before. But the old card would have charged $118.32 in interest the first month and $116.76 the second; after two statements, the interest avoided ($235.08) has already outrun the $186 fee. The balance doesn't even clear the window — $3,386 remains when the promo ends and reverts to 24.9% — yet the transfer path finishes in 3 years 1 month instead of 4 years, costing $7,214.66 all-in versus $9,474.56. That's $2,259.90 saved: $3,274.56 of old-card interest traded for $828.66 of post-promo interest plus the $186 fee.

One honest wrinkle: both paths assume the same $200 payment, so cash out of pocket matches until one finishes. The reported breakeven therefore lands at month 37, when the transferred balance hits zero while the old card would still owe $1,865.72 — the fee was recovered on paper within two months, but you feel the win as eleven payments you never make.

When the balance outlives the promo

As the example shows, a residual balance can survive the window and the transfer can still win — but only because standard balance-transfer cards charge residual interest: the post-promo APR applies to what's left, going forward. Deferred-interest offers — the "no interest if paid in full by…" financing behind many store cards — retroactively charge interest on the entire original amount if anything remains at the deadline. If your fine print says "deferred interest," running long costs far more than shown here.

Prefer to finish inside the window? At 0% the arithmetic is friendly — $6,386 over 15 months is roughly $426 a month — and the target payoff calculator solves for the required payment at any rate.

Two habits that quietly break the math

The schedule assumes the transferred balance only ever shrinks. Two behaviors violate that. First, new spending on the transfer card: purchases usually accrue at the regular purchase APR, and a carried balance typically forfeits your grace period. Second, a late payment: promo terms can end early if you fall behind, and past 60 days delinquent the CARD Act permits a penalty APR on the existing balance. Autopay the minimum, and buy groceries on a different card.

When to skip the transfer

Some situations fail the test before you've filled in a single field. Small balances and fast payoffs: the fee scales with the balance, but savings scale with balance and time — move $1,500 while paying $400 a month and both paths finish in 4 months, the transfer saving all of $26.44 after its $45 fee. Hardly worth a hard credit inquiry. And if the post-promo APR sits well above your current rate while your payment can't clear the balance in time, the reverted months claw back much of the promo's gift. In these cases, adding to your monthly payment often beats transferring — no fee, no new account, no fine print.

How we calculate this

Two parallel amortization schedules share your monthly payment. Path one keeps your balance at the current APR; path two folds the fee into the starting balance, applies the promo APR through the promo months, then switches any remainder to the post-promo APR. Interest accrues monthly at one-twelfth of the annual rate in both. Each month we record cumulative payments per path; the breakeven month is the first month the transfer path's total is lower without ever crossing back, and total savings is the difference in lifetime cost between the two.

Frequently asked questions

Why would a balance transfer ever cost more than just keeping my card?

The fee — typically 3–5% of everything you move — is charged in full the moment the balance transfers, while the interest savings arrive gradually, statement by statement. On a small balance or a fast payoff, those savings never catch up to the fee.

What happens if I don't pay off the balance before the promo APR ends?

On a standard balance-transfer card, only the amount still remaining accrues interest at the post-promo rate, and only from that point forward — nothing retroactive. Deferred-interest financing (common with store cards) is different: any leftover balance triggers back-interest on the full original amount. This calculator models the standard, non-deferred kind.

Does a shorter promo period always mean transferring is worse?

Only if your payoff runs past it. When your payment clears the transferred balance inside the window anyway, extra promo months add nothing — a 12-month offer with a lower fee can beat an 18-month offer with a higher one. Compare the transferred-path payoff time to the promo length to see which case you're in.

Can I put new purchases on the balance-transfer card?

You can, but they usually don't get the promo rate — purchases accrue at the regular purchase APR unless the offer explicitly covers them, and a carried balance generally forfeits your grace period, so that interest starts immediately. Keep the transfer card for paydown only.

Can a missed payment cancel the 0% promo rate?

Yes. Issuer terms commonly end the promotional rate early if you fall behind, and under the CARD Act an issuer can apply a penalty APR to an existing balance once you're more than 60 days delinquent. Autopay for at least the minimum is cheap insurance.

Sources

• Federal Reserve, G.19 Consumer Credit report (Federal Reserve G.19 Consumer Credit report, as of 2026-05-01)
• Consumer Financial Protection Bureau, Credit cards
• Consumer Financial Protection Bureau, What is a balance transfer?