Balance Transfer Calculator

What this calculator is, and when to reach for it

A balance transfer offers something close to a gift: move a balance to a new card and pay no interest for a fixed window, usually in exchange for a fee of a few percent. Used deliberately, it is one of the most effective tools available to anyone carrying card debt, because for the length of the promotion every unit you pay goes entirely to the balance instead of being consumed by interest.

Used passively, it is a way of paying a fee to postpone a problem. The offer has an end date, and what happens on that date is the whole story. If the balance is cleared before the promotional rate expires, the transfer has worked beautifully. If it is not, the remainder reverts to a standard card rate that is often no better than the one you left.

So the calculation is not really "is this offer good?" but "will I clear it in time, and what happens if I do not?" This page answers both, comparing staying put against transferring, counting the fee properly, and showing what the balance costs once the promotion ends.

Reach for it when a transfer offer arrives, when you are choosing between offers with different fees and windows, or when you want to know what monthly payment would be required to finish inside the promotional period.

The number that actually decides it

Divide the transferred balance, including the fee, by the number of promotional months. That is the payment required to clear it in time, and it is the figure worth working out before anything else. If it is comfortably affordable, the transfer is straightforwardly worth doing. If it is not, you are planning to leave a balance behind at the reversion rate.

That does not automatically make the transfer wrong — even a partial clearance saves real interest — but it changes what you are buying. You are purchasing a discount on part of the debt, not an escape from it, and the fee should be judged against that smaller benefit.

The most common failure is arithmetic rather than discipline: people transfer without ever calculating the required payment, then discover at month nineteen that most of the balance is still there.

Where to go next

To see what the same balance costs if you simply pay it down where it sits, use the credit card payoff calculator — it is the comparison every transfer should be measured against. The minimum payment calculator shows the cost of changing nothing at all.

If several balances are involved, or if the required payment is unaffordable, the debt consolidation calculator tests whether a fixed-rate loan with a defined end date would serve better, and the personal loan calculator prices that option directly.

Where clearing debt is a step toward borrowing, the debt-to-income calculator shows how much capacity it would free. The debt payoff journey compares every route in one place.

How the transfer is worked out

Two paths are modelled: staying on the current card at its rate, and transferring at a promotional rate that reverts on a known date.

transferred balance = balance × (1 + fee %)   |   payment to clear in time = transferred balance ÷ promotional months

fee %

the transfer fee, commonly around three percent of the balance

promotional months

how long the reduced rate lasts before reverting

The fee is charged before you save anything

A transfer fee is added to the balance at the outset, so you begin owing more than you did before. On an 8,000 balance a three percent fee is 240, and you start at 8,240. Everything after that has to earn the fee back before the transfer is ahead.

At typical card rates the fee is recovered quickly — 240 is roughly a month and a half of interest at 22.9% — which is why transfers so often make sense arithmetically even when the balance will not be fully cleared. The fee is small relative to what card interest costs.

What happens at the reversion date

On the day the promotion ends, whatever remains begins accruing at the standard rate, which is frequently similar to or worse than the rate you left. There is no grace period and no partial credit for having nearly finished.

This is why the required-payment calculation matters so much, and why a longer promotional window can be worth more than a lower fee. An eighteen-month window at three percent is usually a better instrument than a twelve-month window at two, because the extra six months of zero interest outweigh the extra fee for most balances.

Deferred interest is a different and harsher product

Some offers are not true zero-rate promotions but deferred interest arrangements. Interest accrues throughout the promotional period in the background, and if any balance remains at the end, the entire accrued amount is charged at once.

The difference is enormous. Under a true promotion, missing the deadline leaves you paying interest on the remainder from that point. Under deferred interest, missing it by a single unit can trigger a charge covering the whole period on the whole original balance. Read which one you are being offered before transferring anything.

New purchases and the loss of the grace period

A transferred balance and new purchases are usually treated as separate balances, and purchases often carry the standard rate immediately. Because you are carrying a balance, the grace period that normally makes purchases interest-free is generally lost.

Payment allocation rules complicate this further: issuers commonly apply the required minimum in ways that favour the lower-rate balance, so purchases can sit accruing interest while your payments clear the promotional balance. The clean approach is to treat a transfer card as a repayment vehicle and never spend on it.

What this page assumes

The calculator builds one schedule that keeps the balance where it is at your current rate, and another that adds the transfer fee, charges the promotional rate for the promotional months, then charges the rate that applies afterwards.

The transfer fee is the balance times the fee percentage you entered. The net difference is the current total paid minus the transfer total paid, so the fee is counted through the higher starting balance after the transfer.

Worked examples, step by step

Take an 8,000 balance at 22.9%, and an offer of 0% for 18 months with a 3% transfer fee, against a plan to pay 300 a month either way.

Staying put against transferring

Even though 300 a month does not clear the balance within the promotional window, the transfer still saves 2,722.80 and finishes nine months sooner. Eighteen months of interest-free repayment does an enormous amount of work: by the time the rate reverts, only 2,840 remains, and that clears in a further eleven months at a cost of just 322.82.

This is the case for transferring even when you cannot finish in time. The fee of 240 buys eighteen months during which every unit attacks the balance rather than the interest.

What clearing it in time would take

To finish inside the promotion, the required payment is 8,240 ÷ 18 = 457.78 a month. At that level the entire debt costs 240 and nothing more — an effective rate of about 3% on the original balance for a year and a half.

Comparing the two plans is instructive. Paying 300 costs 562.82 in total; paying 457.78 costs 240. The extra 158 a month saves a further 323 and finishes eleven months sooner, which is a strong return but not a transformative one. Either plan is dramatically better than staying put.

The version that goes wrong

Now suppose the same borrower transfers and pays only the minimum, around 200 a month at first and falling. After eighteen months roughly 4,700 would remain, reverting to a standard rate and taking years to clear.

They would have paid 240 for the privilege of eighteen months of relief and arrived somewhere close to where they started. Nothing about the offer was misleading; the plan was simply never calculated. A transfer is a container for a repayment plan, not a substitute for one.

The vocabulary, on and around this page

Balance transfer

Moving a card balance to another card, usually at a promotional rate for a set period in exchange for a fee.

Transfer fee

A charge for making the transfer, commonly around three percent of the amount moved. It is added to the balance at the outset.

Promotional period

The window during which the reduced or zero rate applies. Its length is usually more important than the size of the fee.

Reversion rate

The standard rate that applies once the promotion ends. It is often similar to the rate you transferred away from.

Required payment

The transferred balance divided by the promotional months: what you must pay monthly to finish before the rate reverts.

Deferred interest

An arrangement where interest accrues quietly during the promotion and is charged in full if any balance remains at the end.

True zero rate

A promotion where no interest accrues at all during the period, so only the remaining balance is affected at reversion.

Grace period

The window in which new purchases incur no interest if the statement is paid in full. Carrying a transferred balance usually forfeits it.

Payment allocation

How an issuer distributes payments across balances at different rates. Rules commonly favour clearing the lower-rate balance first.

Purchase balance

New spending on the transfer card, usually treated separately from the transferred amount and often at the standard rate immediately.

Credit utilisation

The share of available credit in use. A transfer moves utilisation between cards and a new account can lower it overall.

Transfer limit

The maximum an issuer will accept, often less than the full credit limit. It can leave part of a balance behind on the original card.

Hard inquiry

The credit check made when applying for the new card, causing a small temporary dip in a credit score.

Minimum payment

The smallest amount the issuer requires. Paying it during a promotion is the most reliable way to waste the opportunity.

Serial transferring

Moving a balance from one promotional card to another repeatedly. It incurs a fee each time and depends on continued approval.

Effective rate

The total cost expressed as a rate on the original balance. A 3% fee for 18 months of zero interest is a very low effective rate.

Revolving credit

Borrowing with no fixed end date. A transfer does not change this; only your repayment plan gives the debt an end.

Debt consolidation

Combining balances into a fixed-rate loan with a set term. An alternative when the required transfer payment is unaffordable.

Penalty rate

A higher rate applied after a missed payment. On a promotional card it can end the promotion immediately.

Statement balance

The amount owed at the end of a billing cycle. Understanding which balance a payment reduces matters on a card with multiple rates.

Common mistakes, and what this page will not do

• Transferring without calculating the required payment. Divide the balance plus fee by the promotional months before committing. It is the number that decides whether the offer solves anything.
• Paying the minimum during the promotion. It is the most reliable way to reach the reversion date with most of the balance intact, having paid a fee for nothing.
• Not checking for deferred interest. Under that structure, leaving any balance at the end can trigger the entire accrued interest at once. It is a fundamentally different product.
• Spending on the transfer card. Purchases usually attract the standard rate immediately, the grace period is lost, and allocation rules can leave them accruing while you repay the promotion.
• Choosing a low fee over a long window. Eighteen months at three percent usually beats twelve at two, because interest-free time is worth more than the fee difference.
• Missing a payment. A late payment can end the promotional rate immediately and trigger a penalty rate, leaving you worse off than before the transfer.
• Assuming the whole balance will transfer. Issuers set a transfer limit that is often below the credit limit, which can leave part of the debt on the original card at its old rate.
• Closing the old card immediately. Doing so reduces available credit and can raise utilisation, which may weigh on a credit score at the moment you least want it to.
• Relying on transferring again later. Serial transferring costs a fee each time and depends on being approved again, which is not guaranteed once balances are high.

What this calculator leaves out: This calculator assumes no new purchases, one transferred balance, and a payment you keep constant. It does not model deferred interest structures, penalty rates, an issuer’s payment allocation rules across balances, transfer limits, late fees, or whether you would be approved for the offer. Check the specific terms before transferring.

Frequently asked questions