How does the optimizer decide where each balance goes?
First it adds your balances into one total. Then it sorts the cards by interest rate, lowest first. It places as much of the total as fits on the cheapest card, up to that card's credit limit, then fills the next cheapest card, and continues until all the debt is placed. If the debt is larger than the combined limits, the rest stays at the highest rate.
For each layout, current and optimized, monthly interest is every card's balance times its annual rate divided by 12, added up. The gap between the two is the monthly interest saved, and the annual figure multiplies it by 12. That annual number assumes balances stay at today's level, so it is a snapshot of the rate advantage rather than a payoff projection.
The arrangement it finds is the lowest-cost one in theory. In practice, getting there requires balance transfers, which usually carry a fee, need issuer approval, and generally cannot move debt between two cards from the same issuer.
Monthly interest = Σ (Balanceᵢ × APRᵢ ÷ 12) Optimized: fill cards in rate order, each up to its limit Annual interest saved = (Current − Optimized monthly interest) × 12
- Balanceᵢ
- balance on card i
- APRᵢ
- annual rate on card i
- limit
- the most each card can hold
Example: rearranging debt across four cards
Scenario: Say you carry $4,200 on a 28.99% card (limit $5,000), $2,500 on an 18.24% card (limit $8,000), $1,800 on a 22.5% card (limit $3,000) and $600 on a 12.9% card (limit $4,500).
- Total debt$4,200 + $2,500 + $1,800 + $600 = $9,100
- Current monthly interest$101.47 + $38.00 + $33.75 + $6.45 = $179.67
- Fill the cheapest cardCard 4 at 12.9% takes $4,500, its full limit, leaving $4,600
- Fill the next cheapestCard 2 at 18.24% takes the remaining $4,600; Cards 1 and 3 drop to $0
- Optimized monthly interest$4,500 × 12.9% ÷ 12 = $48.38; $4,600 × 18.24% ÷ 12 = $69.92; total $118.30
- Savings$179.67 − $118.30 = $61.37 a month, or $736.44 a year at these balances
Moving the balances to the two cheapest cards would cut interest by $61.37 a month, about $736.44 a year, if the transfers were possible at no cost.
Reaching this layout means transferring $6,000; at an illustrative 3% fee that is $180.00, roughly 2.9 months of the interest saved.
When is a balance optimizer worth running?
You carry balances on cards with very different rates
The wider the spread between your cheapest and most expensive card, the more rearranging can save. If all your rates are similar, the gain will be small.
You have unused room on a low-rate card
Available credit on a low-rate card is the raw material for savings. The optimizer shows how much of your high-rate debt could fit there.
You are considering a balance transfer offer
Running your cards through the optimizer shows the most you could save by moving debt between existing cards. Compare that with what a new transfer card would offer.
Deciding where to put new spending you cannot avoid
If a necessary purchase must go on a card, the optimizer's rate order tells you which card is cheapest to carry it, assuming you have room there.
What mistakes reduce the savings from rearranging balances?
Forgetting transfer fees
Moving a balance usually costs a percentage of the amount moved. The optimizer ignores fees, so compare the fee with the monthly savings to see how many months it takes to break even.
Assuming any card can accept a transfer
Issuers decide whether to approve a transfer and how much of the limit can be used, and transfers between two cards from the same issuer are generally not allowed.
Using the wrong rate
A card can have separate rates for purchases, transfers and cash advances. Enter the rate that would apply to a transferred balance, not just the purchase APR.
Maxing out a card without thinking about scores
Concentrating debt on one card can push it near 100% utilization. Scoring models look at per-card utilization as well as the total, so the cheapest layout is not always the best one for your credit.
Treating the savings as a payoff plan
Lower interest helps only if the debt then gets paid down. Pair a cheaper layout with a fixed payment plan so the savings speed up payoff instead of making room for new spending.
What does the cheapest layout do to utilization on each card?
Moving debt never changes your overall utilization: $9,100 of balances on $20,500 of limits is 44% either way. What changes is the spread. In the optimized layout, Card 4 is completely full and Card 2 is more than half used, while the two high-rate cards drop to zero.
Some people choose a middle ground: move enough to capture most of the savings while leaving each card below a comfortable utilization level. You can test that by lowering a card's limit in the calculator to the amount you would be willing to use and re-running it.
| Card | Current balance | Current utilization | Optimized balance | Optimized utilization | Current monthly interest | Optimized monthly interest |
|---|---|---|---|---|---|---|
| Card 1 (28.99%, $5,000 limit) | $4,200 | 84% | $0 | 0% | $101.47 | $0.00 |
| Card 2 (18.24%, $8,000 limit) | $2,500 | 31% | $4,600 | 57% | $38.00 | $69.92 |
| Card 3 (22.5%, $3,000 limit) | $1,800 | 60% | $0 | 0% | $33.75 | $0.00 |
| Card 4 (12.9%, $4,500 limit) | $600 | 13% | $4,500 | 100% | $6.45 | $48.38 |
| All cards | $9,100 | 44% | $9,100 | 44% | $179.67 | $118.30 |
Terms used on this page
- Credit Utilization
- Credit utilization is the share of your available revolving credit that you are currently using, shown as a percentage. It is calculated by dividing your card balances by your credit limits, both per card and across all cards. Lower utilization generally helps credit scores, and it is one of the factors you can change quickly.
- Balance Transfer
- A balance transfer moves debt from one credit card or loan to another card, usually to take advantage of a low or 0% promotional APR. It can cut interest sharply while you pay down the balance, but most transfers carry a fee, and any amount left when the promotion ends is charged the regular rate.
- Balance Transfer Fee
- A balance transfer fee is a one-time charge for moving debt onto a credit card, usually a percentage of the amount transferred, often with a dollar minimum. The fee is added to your new balance right away, so it is the upfront price of a lower promotional rate and must be weighed against the interest you save.
- APR (Annual Percentage Rate)
- APR is the yearly cost of borrowing expressed as a single percentage that includes the interest rate plus certain required fees, such as origination charges. Because lenders must calculate it the same way under federal Truth in Lending rules, APR lets you compare loan offers on an even footing.
- Debt Avalanche
- The debt avalanche is a payoff strategy where you pay the minimum on every debt and put all extra money toward the balance with the highest interest rate first. When that debt is gone, its payment rolls to the next-highest rate. Mathematically, it usually minimizes total interest and often finishes as fast or faster than other orders.
Credit Card Optimizer: common questions
Should I move my credit card debt to the card with the lowest rate?
If the move is allowed and the fee is small relative to the interest saved, it usually lowers your cost. Compare the transfer fee with the monthly savings to find how many months it takes to break even, and make sure you will keep the balance there long enough. Also confirm that the lower rate would apply to transferred balances, since some cards charge a separate transfer APR.
Can I transfer a balance between my existing cards?
Sometimes. Many issuers allow transfers onto an existing card, often with a fee, but generally not between two cards they issue. Look for a transfer option in the online account or ask the issuer what rate and fee would apply. If a transfer is not possible, you can still get much of the same benefit by directing extra payments to the highest-rate card first.
Is it bad to max out one card to save interest?
It can lower your credit score while the card is near its limit, because scoring models consider per-card utilization. The interest savings are real, though. If you have no big credit application coming up, the trade-off may be acceptable; if you do, a more even spread may be wiser. Paying the concentrated balance down quickly shortens the time the card sits near its limit.
Which card should I pay first if I can't move balances?
Pay the minimums on all cards and send extra money to the highest-rate card. That is the debt avalanche method, and it reduces interest the same way the optimizer does: by shrinking the most expensive balance first. Keep paying at least the minimum on every other card so none of them falls behind while the top-rate card shrinks.
Why does the optimizer ignore transfer fees?
Because fees vary by card and offer, and some transfers have none. The calculator shows the pure rate advantage. To account for a fee, multiply the amount moved by the fee rate and divide by the monthly savings to see how long the move takes to pay for itself. If the break-even point is longer than you expect to carry the balance, the move is probably not worth it.
Does the annual interest saved figure assume I pay nothing down?
Yes. It multiplies today's monthly savings by 12, as if balances stayed the same. As you pay down debt, both interest figures shrink, so the actual savings over a year will be somewhat less, though still meaningful. Think of it as the rate advantage of the new layout rather than a precise forecast of dollars saved over the next year.
What if my debt is more than the limits on my low-rate cards?
The optimizer fills each card in rate order up to its limit, and any debt that does not fit stays at the highest rate. The more room you have on cheap cards, the greater the savings. In that case, a balance transfer offer or a consolidation loan may be worth comparing, since your existing cards cannot absorb all of the high-rate debt.
Should I include a card with a promotional rate?
You can, but the savings shown last only as long as the promotion. Enter the regular rate as well to see the longer-run picture, and use the 0% balance transfer calculator to plan around the deadline. When the promotion ends, the cheapest layout may change, so re-run the optimizer with the regular rate at that point.
Will asking for a higher limit help?
A higher limit on a low-rate card creates more room for cheap debt, which the optimizer would use, and it can lower utilization. A limit request may involve a credit check, so it is worth asking the issuer how they handle it first. A higher limit only helps if the extra room is used for cheaper debt rather than new spending.
Sources
- Credit cards — Consumer Financial Protection Bureau. Accessed October 17, 2026.
- Regulation Z (Truth in Lending), 12 CFR Part 1026 — Consumer Financial Protection Bureau. Accessed October 17, 2026.
- Credit reports and scores — Consumer Financial Protection Bureau. Accessed October 17, 2026.
We cite primary sources: regulators, central-bank data and federal agencies. Worked examples on this page are our own calculations, last checked October 17, 2026. See our methodology.