What this comparison measures
The calculator estimates current-card interest over the promotional months and compares it with promotional-rate interest plus a percentage transfer fee. It is a carrying-cost screen under a constant-balance assumption, not a payoff schedule.
A positive difference is labeled lower estimated cost. A negative difference is labeled higher estimated cost; the page no longer describes an unfavorable transfer as negative savings.
Simplified equations
Current-card cost equals balance × current APR ÷ 12 × promotional months. Transfer cost equals balance × fee percentage plus balance × promotional APR ÷ 12 × months. Difference equals current cost minus transfer cost.
These equations approximate APR as a monthly rate applied to an unchanged full balance. They do not reproduce an issuer's daily-balance calculation or account for declining balances.
Two interpretation checks
With the loaded $6,500 balance, 22% current APR, 0% promotional APR, 3% fee, and 15 months, estimated current cost is $1,787.50 and transfer cost is $195, a $1,592.50 lower-cost scenario.
For $5,000 at 10% current APR versus 12% promotional APR with a 5% fee over 12 months, the transfer costs $350 more under this model. That result must be read as additional cost, not savings.
Material terms outside the model
Actual results depend on payments and timing, the balance subject to the offer, fee minimums or caps, how the fee is financed, daily periodic rates, promotion expiration, post-promotion APR, minimum payments, new purchases, and conditions that can end a promotional rate.
Review the offer and cardholder agreement. A transfer that reduces short-term carrying cost may still leave a balance when the promotion ends.
Primary consumer sources
The CFPB explains that a balance-transfer fee can apply to a zero-percent offer and describes credit-card interest calculations. Review the offer's promotion and fee terms directly.
Use Credit Card Payoff to model payments and remaining balance rather than treating this constant-balance screen as a repayment plan.