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Enter the carried balance before future interest and purchases.
$
Enter the yearly rate shown for this balance category.
% / year
Use the amount you expect to pay every month.
$
Use 12 for one year, 24 for two years, or another whole month count up to 600.
months
Adds to the known recurring payment; zero leaves it unchanged.
$
Keep zero for a spending-freeze payoff plan.
$
Applied once before charges and interest in its selected month.
$
Month 1 is the next modeled cycle.
month
Zero uses the regular APR from the first month.
months
Applies only during the positive intro period above.
% / year
Off by default because issuer formulas vary.
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Plan review

Commitment checks

Use the break-even amount and statement terms before relying on the timeline.
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Repayment mix

See how much of the modeled repayment is principal versus interest.

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A credit card balance changes through three competing flows: new spending and interest raise it, while payments lower it. A payment can feel substantial yet make little progress when it only slightly exceeds the interest and new charges added during the same period.

Annual percentage rate (APR) expresses borrowing cost on a yearly basis, but card interest is applied periodically. Many issuers calculate actual interest from daily balances and may assign different APRs to purchases, cash advances, transfers, or promotional balances. A single monthly estimate is therefore best used for planning and comparison, not statement reconciliation.

Two planning questions lead to different answers. A payment forecast asks how long a chosen monthly amount will take. A target plan asks for the smallest whole-cent monthly payment that clears the modeled balance within a chosen number of months. Both become less favorable when new charges continue, and both improve when extra payments or an early lump sum reduce principal.

Break-even payment
The first modeled month’s interest plus new charges. Paying only this amount prevents initial growth but does not reduce principal.
Promotional APR period
A fixed number of starting months that use the entered intro rate before the regular APR begins.
Minimum due estimate
An optional issuer-style warning cue based on a percentage, a floor, and possibly interest; it is not the statement amount due.

Small changes can compound across a long payoff. Setting new charges to zero, increasing the recurring payment, or moving a lump sum earlier can reduce both interest and time. Promotional financing deserves special care: an unpaid balance may move to the regular APR, and some offers use deferred interest that can be charged retroactively. That behavior is not represented here.

The results are educational estimates, not financial advice. Use the current statement, card agreement, and issuer payoff information for exact payment dates, minimums, balance categories, fees, grace periods, and allocation rules.

How to Use This Tool:

Model one balance and APR category at a time, using the amount currently carried rather than a future statement estimate.

  1. Enter the Current balance and Regular APR for the balance being modeled.
  2. Choose Forecast my monthly payment and enter the amount you expect to pay, or choose Solve for a payoff target and enter a whole-month horizon from 1 through 600.
  3. Open Advanced to add a reliable extra monthly payment in payment mode, recurring new charges, a one-time lump sum and month, or an intro APR period. Keep new charges at zero for a spending-freeze comparison.
  4. Enable Estimate minimum due only when the percentage, floor, and interest treatment roughly match the issuer’s method. Continue to use the statement minimum for actual payment compliance.
  5. Read the projected payoff time or required payment, then check modeled interest, break-even payment, promotional balance, and warning cues against the statement.

Interpreting Results:

Payment used is the regular monthly commitment in the simulation; a lump sum is shown separately in its scheduled month. Total paid combines recurring payments and the lump sum, while Modeled interest is the monthly-model cost included in that total.

  • New charges modeled means recurring spending is added before interest each month.
  • Promo window ends first means a balance remains after the final intro-rate month and then uses the regular APR.
  • Near minimum due means the payment is no more than 110% of the optional estimated minimum.

A valid projection still may not match the issuer’s payoff quote. Compare the first schedule rows with the statement’s actual interest and balance movement; a material mismatch usually means the monthly single-balance assumptions are too simple for that account.

Technical Details:

The model advances in whole monthly periods and stores money as integer cents. In each month it applies a scheduled lump sum to the opening balance, adds recurring charges, calculates interest at the active APR, and then applies the recurring payment. The last payment is reduced so it cannot overpay the amount due.

Formula Core:

The active APR is divided by 1,200 because it is entered as a yearly percentage and the simulation uses twelve monthly periods.

rm=APR1200 Bm*=max(0,Bm−1−Lm)+C Im=roundToCents(Bm*×rm) Pm=min(P,Bm*+Im) Bm=max(0,Bm*+Im−Pm)

B is balance, L is the lump sum applied in month m, C is recurring new charges, I is interest, and P is the recurring payment. Intro APR applies when the month number is less than or equal to the selected intro-period length; later months use regular APR.

Payment mode uses monthly payment plus extra payment and simulates no more than 600 months. Target mode searches whole-cent payment amounts and returns the smallest amount that clears the balance within the selected horizon.

RuleExact behavior
Break-even paymentFirst-period interest plus recurring new charges, after any month-one lump sum
Payoff failureStops when recurring payment is no greater than interest and no lump sum applies, or when 600 months expire
Target paymentLowest whole-cent amount that pays off within 1 to 600 months
Promo switchIntro APR through month n; regular APR from month n + 1
Near-minimum warningPayment ≤ 110% of the optional estimated minimum due

The optional minimum-due estimate uses the first modeled balance after a month-one lump sum and new charges. Percent-only mode takes the entered percentage of that balance. Interest-plus-percent mode adds first-period interest. The result is raised to the entered floor when needed and capped at the amount due.

MinimumEstimate=min(AmountDue,max(Floor,PercentAmount+OptionalInterest))

Interest rounds to the nearest cent every month, and target search also works in whole cents. The currency is fixed to US-dollar formatting; no exchange-rate conversion occurs.

Accuracy Notes:

Actual statements can diverge because the model uses one balance, one active APR at a time, and monthly interest.

  • Many issuers use average daily balance and daily periodic rates rather than APR divided into twelve equal monthly periods.
  • Fees, grace periods, payment dates, compounding conventions, multiple balance categories, and issuer allocation rules are omitted.
  • The promotional-rate path does not model retroactive deferred interest or loss of an offer after a late payment.
  • The optional minimum due is a warning estimate. Paying the statement minimum by its due date remains the authoritative requirement.

Worked Examples:

Solve a three-month target

A $1,000 balance at 12% APR with no new charges, lump sum, or promotional period requires a modeled payment of $340.03 to clear within three months. Monthly interest rounds to $10.00, $6.70, and $3.37, so total modeled interest is $20.07. The final recurring payment falls to $340.01 because only that amount remains due.

References: