Balance Transfer Calculator

The two costs being compared

Leave the balance where it is and it charges your current APR every month for the whole promo window - interest that grows as the unpaid balance compounds on itself. Move it and you pay the transfer fee up front, then nothing in interest for the promo period. Those are the only two money flows the page models.

So the comparison is simple: the interest the old card would have charged over that window versus the fee the new card charges to stop it. Whichever is smaller is the cheaper path on the money, and everything else - the monthly payment, the balance, the length of the window - is held equal so the fee and the avoided interest are the only things allowed to differ.

When the fee wins and when it loses

A 3% fee on a balance at 22.5% APR pays for itself in well under a year, because 22.5% of the balance over a year is far more than 3% charged once. The transfer almost always wins when the promo is long and your current APR is high, which is the usual selling situation - and the case where the arithmetic genuinely favors the move.

But a short promo or a low existing rate can flip it: if the window is only a few months, the interest you avoid may be less than the fee you pay to avoid it. The page shows the actual crossover on your numbers instead of assuming the promo is always a steal, which is what separates a real comparison from a marketing claim.

The honest limit of the comparison

This page compares the two paths only for the promo window - it does not model what happens to the remaining balance after the 0% rate ends, when the new card usually goes back to charging interest too. That makes it a clean fee-versus-interest comparison, not a full multi-year plan.

The limit cuts both ways. A transfer can look great inside the window yet leave a large residual that starts accruing at the new card’s standard rate, while staying put has no such cliff. Read the result as the answer to one specific question - is the fee worth the interest saved in this window - rather than a verdict on the whole balance’s future.

The payment decides how much either path costs

Both sides of the comparison pay exactly the same amount every month. That fairness is what makes the answer mean something - the only money difference is the interest the old card accrues versus the fee the new card charges. But the size of that payment is part of the math: the faster you pay, the less interest the old card has time to accrue before the window closes, while the transfer fee stays fixed however fast you go.

So the same fee and the same APR can land on different verdicts purely because of how quickly the balance is cleared. Pay slowly and the avoided interest grows, widening the transfer’s edge; pay quickly enough to clear the balance inside the promo and the fee becomes the entire cost of the transfer - which is why a transfer that saves a lot at one payment can look like a near-tie at another.

What the fee costs per month of window

The fee is charged once, but it buys months, and dividing one by the other is the only way to compare it with an interest rate. A 3% fee over an 18-month window is 0.167% of the balance a month; the 22.5% APR it replaces is 1.875% a month. The trade in one line: about a sixth of a percent to stop paying nearly two.

The same division shows where the trade stops working. Halve the window and the monthly price of the fee doubles to 0.333%; cut it to three months and the fee costs 1% of the balance a month, close enough to the interest it avoids that the comparison has to be run on your numbers rather than assumed. That is why promo length sits beside the fee field here: they are two halves of one price.

The counterexample the arithmetic produces: a 5% fee over six months is 0.833% a month against an 18% APR, which is 1.5% a month. The transfer still wins on money, but by a margin small enough that one missed payment or a balance that does not clear inside the window erases it.