Balance Transfer Calculator

What you enter

• Balance: What you owe on the card today. Your statement balance is the right figure.
• Interest rate: The APR the card charges you now. It is on your statement, often as the “purchase APR”.
• Monthly payment: What you put toward this debt each month, in total. After a transfer this same amount is split across the two cards rather than added to — that is what makes the comparison fair.
• How much of your balance can move: Leave this on “All of it” unless you have already been given a credit limit — most people weighing up an offer have not applied yet. The credit limit box then fills itself in and locks, showing the limit the new card would need, so you can see what the assumption actually costs in credit. Choose “Only up to a credit limit” to type your own instead.
• Credit limit: The credit line on the new card. The transfer and its fee both have to fit inside it, so a limit exactly equal to your balance still leaves the fee behind — which is why typing your balance here is not the same as saying it all moves. Switching from “All of it” starts you at the figure that would cover everything, so the natural edit is to lower it.
• Transfer fee: A percentage of the amount you move, charged to the new card. Most offers sit between 3% and 5%.
• 0% period: How many months the card charges 0% on the transferred balance. A “15-month offer” means 15 statement cycles, so the go-to rate first applies in month 16.
• APR after the 0% ends: The go-to rate. This is the number people skip past when they apply, and it is the one that decides whether the offer is worth taking if you cannot clear the balance in time.
• Minimum payment: The smallest payment each card will accept in a month, entered as a percentage or a flat dollar amount. It starts at 1%, the common shape of an issuer’s rule. Whichever card you are not attacking still has to receive this, so it comes out of your monthly payment before the rest is put to work. Enter 0 to leave minimums out of the sums entirely.

Understanding your results

The headline is the difference in what you pay in total, across both cards, from today until the debt is gone. That figure already has the transfer fee taken out of it, so it is what you actually come out ahead by — not the interest saved before costs.

A green result means transferring is the better move. An amber one means it still saves you money, but with a catch worth reading: either the new card could only take a small part of your balance, or so much is left when the 0% ends that the go-to rate takes back most of the saving. A red result means the offer costs you more than staying put, which usually happens when your current rate is already low or the promotional period is short.

The chart shows both paths on one axis. Switch it to Interest and the argument becomes obvious: the transfer line runs flat through the promotional period, then kinks upward the month the go-to rate lands. On the Balance view the transfer line starts slightly higher than the other one. That step is the fee, and it is drawn rather than hidden.

When the limit is smaller than your balance

The calculator assumes the whole balance moves unless you tell it otherwise, because until you apply you generally do not know what limit you will be given. On that setting the credit limit box shows what the assumption implies — your balance plus the fee — rather than leaving you to guess at it. If you do know your limit, choose “Only up to a credit limit” and everything below applies.

Issuers rarely give you a limit large enough to take a whole balance, and the fee is charged to the new card too, so it eats into the same credit line. If your limit is $5,000 and the fee is 3%, the most that can move is $4,854 — the transfer plus its $146 fee comes to exactly $5,000. That is also why entering your balance as the limit is not a way of saying “it all moves”: the fee has nowhere to go, so it stays behind on the old card.

What is left behind stays on your old card at your old rate, and your monthly payment now has to cover two cards. Which one you attack first matters more than it looks. Paying the higher rate first is the usual advice and it is usually right, but it can misfire here: a 0% balance costs you nothing today, so the rule sends every spare pound to the old card and leaves the transferred balance untouched — sitting there waiting for the go-to rate to land on all of it. Whether that is the cheaper choice depends on your rates and how long the promotional period runs.

The reason paying the higher rate first can lose here is worth a moment, because it looks wrong. What a payment is really worth is not this month’s interest rate — it is all the interest that dollar never has to accrue between now and the day the debt clears. Rates compound, so that depends on the rate and on how long the dollar has left to work.

Take a $1 paid in the first month of a payoff running about thirteen years. Put it on a 12% card and it saves you roughly $3.95. Put it on a card charging 0% for eighteen months and 22.99% after that, and it saves about $14.17 — nothing at all for a year and a half, then a much higher rate for the remaining eleven years. The second dollar is worth over three times the first, and “pay the highest rate” sends it to the wrong card.

That is not an argument against paying the highest rate first. It is the right rule almost always, because almost no rate change is knowable in advance — when your issuer reprices a card you find out afterwards, and today’s rate is the best guess you have about tomorrow’s. A promotional rate is the exception: the date it ends and the rate that follows are both in the agreement you signed. So the calculator runs both orders, reports the cheaper one, and tells you which it was.

Once the 0% ends there is no longer a decision to make. Both balances are ordinary debt, so the payment always goes to the higher rate first — which is the avalanche method, applied to two cards instead of a longer list. The promotional period is the only stretch where that rule does not settle the question, because a 0% balance looks free right up until the month it stops being free.

Reading the month-by-month breakdown

The breakdown gives each card its own columns — what you paid it, what it charged you, and what is left — with the promotional months tinted. The “Going to” column names the card taking whatever is left of your payment that month. The other one receives only its minimum, so the two columns always add up to the payment you entered.

Why the transfer card’s payment jumps when the 0% ends

This is the one figure in the table that catches people out, and it is worth understanding rather than skipping. A card’s minimum is that month’s interest plus a percentage of the balance. While the promotional rate runs there is no interest on the transferred balance, so its minimum is just the percentage. The month the go-to rate lands, interest appears and the minimum jumps by exactly that much.

Take a transfer card sitting at about $4,200 with the old card being attacked first. Through the 0% period its minimum is around $42 a month, all of it coming off the balance. The month the rate changes to 20%, $70 of interest is charged, so the minimum becomes about $112 — and because your total payment has not moved, the old card’s share drops from roughly $258 to $188.

The larger payment is not faster progress. The transferred balance still falls by about the same $42; the extra $70 is interest. So a promotional rate running out costs you twice — once in interest on the transferred balance, and again by pulling money away from the card charging you the most. That second cost is the one nobody expects, and it is the strongest argument for clearing the transferred balance before the offer expires.

What it does not model

The minimum payment floor

Minimum payments themselves are modelled: every card carrying a balance receives its minimum in every month shown, and the rest of your payment goes to the card being cleared. That matters more than it sounds, because without it the calculator would happily leave a transferred balance untouched for two years — and missing a payment on a promotional card ends the 0% rate at most issuers, which would undo the whole exercise.

When your payment cannot cover what the transfer card asks for, the calculator says so instead of showing a payoff. That is not a technicality. A plan that quietly skips a payment is not a slower payoff, it is a missed one, and a missed payment on a promotional card ends the 0% at most issuers — so the projection would be describing an offer you no longer have. The figure it reports is what is actually required, so you can see how far short the payment falls.

This applies whether the balance was split or not. If the whole balance moved there is one card to feed rather than two, but the promotional rate is no less forfeitable for being the only thing at stake.

The two ways of entering a minimum are read differently, on purpose. A percentage means that share of the balance on top of the month’s interest, which is how issuers write the rule — a percentage on its own would not cover the interest on any card above about 12% APR, and the untouched card would sit frozen or grow. A dollar amount is taken exactly as entered.

That difference matters if you use the dollar option. Issuers apply their fixed figure — often $25 to $35 — as a floor underneath the percentage rule rather than instead of it, so a flat minimum smaller than a card’s monthly interest will let that balance grow. The calculator shows you that happening rather than hiding it, but it is a consequence of the number you entered, not a forecast of what your card would do. If you are not sure, the percentage is the safer choice.

Rates that change on their own

Both APRs are held at the figures you entered, apart from the one scheduled change when the promotional period ends. Real card rates are variable: an issuer can reprice a card, and the rate that made your old card the expensive one this year may not be the one it charges next year. Nothing here forecasts that, because nobody sensibly can — which is exactly why the promotional step is modelled and a repricing is not. One is a date in your card agreement; the other is a letter that arrives with a month’s notice.

The practical consequence is that the payment order suggested here is right for the rates you entered, not for all time. If either card is repriced, come back and run it again — the answer can move, and on a long payoff it can move a long way.

New spending

Nothing is added to either card after the transfer. If you keep spending on the old card you will be paying it down and running it up at the same time, and the payoff date here will be optimistic. Balance transfer cards also often charge a separate, higher rate on purchases, and a payment usually has to clear the highest-rate balance first, so spending on the new card can leave your transferred balance sitting untouched. Our Credit Card Payoff Calculator handles a card you are still spending on.

The fine print on the offer

Some issuers cap transfers below your full credit line, or set a minimum fee such as “3% or $5, whichever is greater”. Some apply the transfer fee at the purchase rate rather than the promotional one. Transfers between cards from the same issuer are usually not allowed at all, and the promotional rate typically has to be used within the first few months of opening the account. Check the offer’s terms before you count on the figure here.

Making the most of a transfer

The point of a 0% period is that every payment goes to the balance instead of the interest, so the debt falls faster than it ever did before. That only happens if you keep paying at least what you were paying already. Dropping to the minimum because the rate is 0% wastes the offer, and you arrive at the end of the promotional period with most of the balance intact and a high rate waiting.

When the calculator shows a balance still owing at the end of the 0% period, it also shows the monthly amount that would clear it in time. That is the number to aim at. If it is out of reach, the offer can still be worth taking, but go in knowing the go-to rate is part of the deal rather than a detail at the end of it.

One more thing worth knowing: applying for the new card means a hard search on your credit file, and opening it lowers the average age of your accounts. Both effects are small and short-lived. The larger effect usually runs the other way, since moving a balance onto a new credit line lowers your overall credit utilization.