How this instrument works
A balance transfer moves revolving debt from one credit card to another, usually one offering a temporary low or 0% introductory APR, so the cardholder stops paying interest at the old rate for a stretch of months. Card issuers recoup that discount with an upfront transfer fee, typically 3% to 5% of the amount moved, charged once regardless of how the balance is later paid down.
This instrument compares two costs directly: the interest the old card would have charged over the months specified, computed as a straight simple-interest line rather than a compounding one, against the one-time fee the new card charges to accept the balance. That straight-line shortcut is deliberate — it treats the balance as flat for the whole period, which overstates the interest saved for anyone who plans to keep making payments and shrink the balance, since a shrinking balance accrues less interest each month than a static one would.
People reach for this math before opening a transfer offer, not after — it answers whether a card's fee is small enough against the interest at stake to bother applying, given a credit score that already qualifies for the intro rate. It says nothing about the standard APR that resumes once the introductory period ends, which is the detail that turns a good transfer into a costly one when the balance is not cleared in time.
- Enter the balance you'd move in the field labeled Balance to transfer, $.
- Enter the rate on the card carrying that balance now, using Current card's APR, %.
- Set Months you'd otherwise carry the balance to the payoff timeline you expect on the old card.
- Enter the new card's Balance transfer fee, % — most issuers charge 3% to 5%.
- Read Interest avoided, Transfer fee charged, and Net savings — the last is what the move is worth on paper.
Worked example — a $5,000 balance at 22% APR
Take a $5,000 balance sitting on a card at 22% APR that would otherwise take a year to pay off. The monthly rate is 22 divided by 100 divided by 12, so interest avoided is $5,000 times 0.018333 times 12, which comes to $1,100 — what staying on the old card for those twelve months would have cost in interest alone.
The receiving card charges a 3% transfer fee, so the one-time cost is $5,000 times 0.03, or $150. Net savings is $1,100 minus $150, landing at $950. That figure holds only under the model's flat-balance assumption; paying the debt down faster than twelve months would lower the interest-avoided figure and could shift net savings either way depending on the new payoff pace.
Questions
Does this account for paying down the balance during the period?
No. The interest-avoided figure assumes the full balance sits untouched for the whole period, the same simplification a 0% intro offer's fine print implicitly invites a cardholder to check against their own payoff plan. Real monthly payments shrink the balance and therefore the interest a static comparison credits as avoided, so an active payoff plan saves less than this figure shows.
How is this different from a debt consolidation loan calculator?
A balance transfer keeps the debt on a credit card and defers interest for a limited introductory window; a consolidation loan replaces revolving debt with a fixed-term installment loan carrying its own rate for the whole payoff. This instrument only prices the transfer-and-fee trade — it does not model a loan's amortization schedule or a longer repayment horizon.
What happens if the balance isn't paid off before the intro period ends?
The card's standard APR applies to whatever balance remains, often well above the rate on the original card, which is the single biggest way a transfer stops paying for itself. This tool only compares costs during the window entered in Months you'd otherwise carry the balance — it does not project what happens after that window closes.
Why does a 3% fee sometimes cost more than the interest it avoids?
For a small balance carried only a couple of months, the flat percentage fee can exceed the interest a short intro period would have skipped — the formula shows this directly whenever Net savings turns negative. Balance transfers tend to make the most sense for larger balances carried over longer stretches, where the one-time fee is small next to the interest that would otherwise accrue.
Does a lower APR always mean a better balance transfer offer?
Not by itself — a 0% card with a high transfer fee can cost more than a low-fee card charging a small ongoing rate, depending on the balance size and the months involved. Compare offers by running each one's real APR, fee, and expected payoff period through this instrument rather than by reading the headline rate alone.
Do I need good credit to qualify for a balance transfer card?
Most 0% and low-APR transfer offers are reserved for applicants with good to excellent credit, since issuers are extending an interest-free grace period as an acquisition cost. This instrument assumes an offer has already been extended; it prices what the offer is worth, not whether an application will be approved.
References
- Consumer Financial Protection Bureau — Credit cards
- Federal Reserve — Consumer credit (G.19) statistical release
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.