Last reviewed 2026-09-02

Methodology: how this calculator works

Every number on this site comes from the formulas below. They are implemented once, in a small open engine with unit tests, and the same code produces the calculator results, the schedules and the charts. Where our results differ from other calculators, the reason is stated in the last section.

1. What the calculator models

You enter one or more current balances with their APRs and what you pay now, the terms of a new card (intro APR, intro period, transfer fee, go-to APR, optionally the credit limit and how long the transfer takes to post), and the monthly payment you plan to make. The engine then runs four scenarios month by month:

1. Keep paying as now. Each card keeps its own balance, APR and current payment. No consolidation.
2. Balance transfer. The balances move to the new card, the fee is added, the intro APR applies for the effective intro period, then the go-to APR applies to whatever is left. Your planned payment is applied every month.
3. Same payment, no transfer. Your planned payment is applied to the current cards, highest APR first, with no fee. This is the honest baseline for "was the transfer worth it": it separates the effect of paying more from the effect of transferring.
4. Personal loan. The total balance is refinanced into a fixed-payment loan at the APR and term you choose, with an origination fee either deducted from the proceeds (so the loan is grossed up) or added to the principal.

2. Interest each month

By default interest is charged monthly on the opening balance at the monthly periodic rate, APR ÷ 12. For a $5,000 balance at 24% that is $100 in month one.

Card issuers actually compute interest daily on the average daily balance. An optional daily compounding mode uses the equivalent monthly factor (1 + APR ÷ 365)365 ÷ 12 − 1, which is 1% to 2% higher over a year. We default to monthly because it matches the way most published calculators and issuer disclosures illustrate examples, and we say so here rather than leaving you to guess. WalletHub uses daily; NerdWallet, Forbes, Experian, Credit Karma and The Motley Fool use monthly.

3. The transfer fee

fee = max(fee% × amount transferred, minimum fee), then capped if the issuer sets a cap. The default is 3% with a $5 minimum. Most US cards charge 3% to 5%; some cards charge 3% inside an early window and 5% after it; a few credit-union and regional cards (for example Banco Popular in Puerto Rico, 2% with a $10 cap) are lower.

The fee is added to the transferred balance on day one. It is part of the promotional balance, so it is interest-free during the intro period and is charged at the go-to APR if any of it is still there when the intro period ends. Discover's own example makes this explicit: transfer $1,000 with a 5% fee and you owe $1,050. A second mode models issuers that post the fee to the purchase balance instead (Citi is the common example); in that mode the fee accrues interest at the purchase APR from the first month.

If you enter a credit limit, the amount transferred is capped so that amount + fee ≤ limit. Anything left stays on the old cards at their APRs and is included in the transfer scenario's schedule.

4. The intro period and the posting lag

On almost every US card the intro APR clock starts at account opening, not when the transfer posts. Transfers typically take 5 to 21 days (Amex says up to six weeks). We therefore reduce the intro period by the posting lag: effective months = floor(intro months − lag days ÷ 30.44). With the default 14-day lag, an 18-month offer gives 17 effective months of 0%.

The old cards keep charging interest until the transfer posts. That amount, balance × APR ÷ 365 × lag days per card, is shown as "interest while the transfer is in transit" and is counted in the total cost of the transfer scenario. It is billed on the old card's final statement.

Under Regulation Z (12 CFR 1026.55) a promotional rate must last at least six months and can only be revoked early if a payment is more than 60 days late. The engine does not silently end the promo for a single late payment, because US cards cannot do that; UK cards can, and the UK preset says so.

5. Minimum payments

The default minimum is max($40, 1% of the balance + this month's interest and fees), never more than the balance. That matches the CFPB's 2025 finding that most issuers charge 1% of the statement balance plus interest and fees, with dollar floors of $15 to $50 and $40 the most common, and it matches the Chase and Citi cardmember agreements (Citi's floor is $41). Presets exist for flat 2% and 3% minimums and for Québec's statutory 5% floor.

The "minimum only" projection applies this formula every month until the balance is cleared, and reports the total interest and the payoff time. If the minimum cannot even cover interest, the projection says the balance never clears.

6. How payments are split between balances

When a card carries balances at different rates (a 0% transferred balance, the fee at the purchase APR, new purchases, or balances left on the old cards), the split matters:

• United States (12 CFR 1026.53): anything you pay above the minimum goes to the highest-APR balance first. The minimum itself is allocated at the issuer's discretion, and in practice it goes to the lowest-APR balance, which is usually the promotional one. The engine models exactly that.
• United Kingdom: every payment goes to the highest-APR balance first.
• Canada: issuers may choose highest-APR-first or pro-rata (SOR/2009-257 s.4). The Canada preset uses pro-rata, the more conservative assumption.

One consequence worth knowing: if you make purchases on a card that is carrying a transferred balance, the purchases usually get no grace period and your minimum payment chips away at the 0% balance while the purchases keep accruing. The calculator assumes no new purchases on the new card and says so in the results.

7. The headline outputs

Payment needed to clear the balance inside the intro period

The level monthly payment that takes the opening balance (transfer + fee) to zero in the effective intro months. At 0% that is simply opening balance ÷ months: $5,150 over the 17 months left once a 14-day posting lag is taken off an 18-month offer is $302.94. For a non-zero promo rate the standard amortisation formula P = r × B ÷ (1 − (1 + r)−n) is used with r = intro APR ÷ 12.

Net saving

net saving = total paid in "same payment, no transfer" − (total paid in "balance transfer" + transit interest). Because the fee is inside the transferred balance, it is automatically part of "total paid". We also show the saving compared with your current payments, but the verdict is not based on it, because that comparison rewards paying more, not transferring.

The verdict

• Worth it based on these numbers: net saving is above $50 and above 10% of the interest you would otherwise pay.
• Marginal: net saving is positive but below that threshold. The saving is real but small enough that a hard inquiry, a missed payment or a slightly worse offer would erase it.
• Not worth it based on these numbers: net saving is zero or negative.

Break-even figures

• Break-even fee: the fee percentage at which net saving reaches zero, everything else unchanged. Found by bisection between 0% and 25%. If a transfer does not help even at 0%, this reads 0%.
• Break-even month: the first month in which the cumulative interest avoided (baseline interest minus transfer interest) exceeds the fee plus transit interest.
• Payment at which the verdict flips: the monthly payment above which the transfer stops saving money (the debt clears so fast that the fee outweighs the interest avoided), or, when the transfer is not worth it at your payment, the payment below which it would start to be. Found by bisection.

Remaining balance when the intro period ends

Shown at three payment levels: your planned payment, the minimum only, and the "clear in time" payment. The first month's interest at the go-to APR on the remaining balance is shown next to it, so the size of the cliff is visible.

8. Personal loan comparison

Fixed monthly payment from the same amortisation formula over the chosen term. With a deducted origination fee the loan principal is balance ÷ (1 − fee%) so that the proceeds cover the card balances; with an added fee the principal is balance × (1 + fee%). Default tier APRs are NerdWallet's September 2026 averages: excellent 14.87%, good 19.59%, fair 23.84%, bad 27.28%. They are illustrations, not offers.

8a. India loan balance transfer calculators

The India loan tools (home, personal, car, education, loan against property) use the same month-by-month reducing-balance engine with a level EMI. The existing loan is simulated at its rate for the remaining months, or at the EMI you enter. The new loan is simulated on the outstanding principal (plus any fees you choose to finance) under two repayment paths: same tenure (a lower EMI over the same months) and same EMI (the old EMI kept, so the loan clears sooner). Switching costs are itemised: processing fee with any floor, cap or flat amount, foreclosure charge on the old loan, and other one-off charges such as MOD or stamp duty, legal, valuation and CERSAI. GST at the rate you enter (18% by default) is added to the processing fee and the foreclosure charge; interest on a loan is exempt, unlike the interest component of a credit card EMI. A foreclosure quote that already includes GST can be flagged as such and is split back into charge and tax.

Net saving is the total paid on the old loan minus the total paid on the new loan minus the costs paid from pocket. Break-even month is the first month in which the interest saved so far covers the pocket costs; this is the same definition as the card calculator and, unlike the shortcut of dividing costs by the EMI difference, it does not flatter a transfer that stretches the tenure. Break-even rate is the new rate at which the same-tenure path nets zero, found by bisection. The verdict is bad when the net saving is zero or negative, marginal when the break-even falls in the second half of the new tenure or the saving is under 1% of the outstanding, and good otherwise. A moratorium on an education loan is modelled as simple interest for the moratorium months, either capitalised into the principal or serviced monthly. Section 80E is an optional after-tax line that scales the interest saving by one minus the tax slab.

The debt consolidation tool compares three paths over the loan's horizon: paying as now (cards with no payment entered pay the minimum due, 5% of the outstanding with a Rs 200 floor), paying the loan EMI across the cards highest rate first, and the loan itself. Each path is charged with what is still owed at the end of the horizon, so a path that never clears is not made to look cheap. The gold loan LTV tool values gold at the 22 carat reference price scaled by purity and applies the RBI tiers of 85%, 80% and 75%; for bullet loans the tier applies to principal plus simple interest to maturity, so the eligible amount is solved rather than multiplied. The worked examples in the India guides are reproduced in the unit tests.

9. Defaults and where they come from

10. Where we differ from other calculators, and why

We ran the same scenario ($5,000 at 24%, $300 a month, 3% fee, 0% for 18 months, 24% after) through the major calculators and compared:

• Interest without a transfer: $1,143.34 over 21 months. Experian, Forbes Advisor, CreditCards.com and The Motley Fool agree to the dollar. NerdWallet shows $1,003 because it assumes you would pay exactly enough to clear the debt in 18 months ($333.51 a month) rather than the payment you entered.
• Saving from the transfer: $993. Forbes ($993), CreditCards.com ($993.34) and The Motley Fool ($992.60) agree. Credit Karma ($992.60) agrees here but, with a lower $150 payment, it ignores the interest charged after the intro period and overstates the saving by about $546.
• Payment to clear inside the intro period: $302.94. Credit Karma and Forbes print $286.11 because they divide by the full 18 months; this site divides by the 17 months left once the posting lag is counted. Discover suggests $344 because its offer is 15 months, not 18.
• Daily versus monthly compounding. WalletHub reports $153 of post-intro interest at $200 a month where the monthly method gives $151. We show the monthly figure by default and offer daily as an option.
• Month counting. With a $150 payment The Motley Fool reports 37 months to payoff; the exact schedule needs a twentieth post-intro payment, so we report 38 months with identical interest ($545.93).
• Bankrate could not be run automatically (its calculator sits behind a bot check). We make no claim about how it treats the fee.

11. What the calculator does not model

• Penalty APRs after a late payment, annual fees on the new card, and the effect of a hard inquiry on your score. These are discussed in the guides but are not in the arithmetic.
• New purchases on the new card (assumed none).
• Trailing interest quirks on the old card's final statement beyond the transit-interest estimate.
• Taxes, rewards, and any card benefits.

The engine and its tests are part of this site's source. If you find a case where the numbers look wrong, the contact page explains how to report it.