Minimum Payment Trap CalculatorFree online financial calculator — instant results, no sign-up
Compare a percentage-of-balance minimum payment with a fixed monthly payment.
Estimates only, based on the inputs and assumptions shown. This is not financial, investment, tax, or legal advice. Prices, rates and local rules may change; crypto scenarios do not predict returns. Confirm important decisions with a qualified professional.
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About the Minimum Payment Trap Calculator
The Minimum Payment Trap Calculator compares paying a percentage-of-balance minimum, subject to a dollar floor, with paying a fixed amount each month. It shows how a shrinking minimum payment can extend repayment and increase interest, even when you make every payment on time. Use the two plans to compare payoff time and total interest on the same starting debt.
- Balance ($)
- The starting debt to repay, in dollars, with a default of $5,000.
- Annual rate (%)
- The annual interest rate applied to the debt, expressed as a percentage, with a default of 24%.
- Minimum balance percentage (%)
- The percentage of each month's starting balance used to calculate the minimum payment before applying the dollar floor, with a default of 3%.
- Minimum payment floor ($)
- The lowest scheduled monthly payment under the minimum plan, in dollars, unless the remaining balance plus interest is smaller, with a default of $35.
- Fixed comparison payment ($)
- The constant monthly payment used for the comparison plan, in dollars, with a default of $200.
Formula and method
r = a / (100 × 12); p = m / 100. For each plan, B₀ = B. In month t: Iₜ = r × Bₜ₋₁. Minimum plan: Pₜ = min(Bₜ₋₁ + Iₜ, max(p × Bₜ₋₁, F)). Fixed plan: Pₜ = min(Bₜ₋₁ + Iₜ, C). After payment: Bₜ = max(0, Bₜ₋₁ + Iₜ − Pₜ). Payoff months N is the first month with Bₙ = 0; total interest T = Σ Iₜ for t = 1 through N.
- BStarting balance in dollars.
- aAnnual rate entered as a percentage.
- rMonthly interest rate expressed as a decimal.
- mMinimum balance percentage entered as a percentage.
- pMinimum balance percentage expressed as a decimal.
- FMinimum payment floor in dollars.
- CFixed comparison payment in dollars.
- tMonthly payment period, starting at 1.
- BₜBalance remaining after month t's payment, calculated separately for each plan.
- IₜInterest charged in month t, in dollars.
- PₜActual payment in month t, capped at the balance plus that month's interest.
- NNumber of monthly payments required to repay a plan.
- TTotal interest accumulated through payoff, in dollars.
Simulate the plans separately from the same starting balance. Each month, calculate interest using the annual rate divided by 12. For the minimum plan, calculate the percentage payment from the balance before that month's interest and use the larger of that amount and the payment floor; for the fixed plan, use the fixed comparison payment. Cap either payment at the amount owed, update the balance, and repeat until payoff, counting months and accumulating interest. With the default inputs, the minimum plan takes 201 months and incurs $8,441.75 in interest; the fixed plan takes 36 months and incurs $2,000.56 in interest.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Balance5000 $
- Annual rate24 %
- Minimum balance percentage3 %
- Minimum payment floor35 $
- Fixed comparison payment200 $
Results
- Minimum-plan months201
- Minimum-plan interest$8,441.75
- Fixed-plan months36
- Fixed-plan interest$2,000.56
How to use the Minimum Payment Trap Calculator
- 1Enter your starting balance in dollars and annual interest rate as a percentage.
- 2Enter the minimum balance percentage and dollar floor that you want to model.
- 3Enter a fixed monthly payment you could maintain throughout repayment.
- 4Run the comparison and review payoff months and total interest for both plans.
- 5Adjust the fixed payment to explore the trade-off between monthly affordability and repayment cost.
Reading your result
The minimum-plan months row shows how many payments are needed when the payment declines with the balance until the floor applies: 201 months with the defaults. The minimum-plan interest row shows cumulative interest, excluding the original principal: $8,441.75. The fixed-plan months row shows the payoff time when the comparison payment stays constant: 36 months. The fixed-plan interest row shows cumulative interest under that schedule: $2,000.56. In this example, paying $200 monthly instead of the modeled minimum pays off the debt 165 months sooner and saves $6,441.19 in interest.
Limitations
This is a simplified monthly repayment model, not a credit-card statement forecast. It assumes a constant rate, payments at the end of each monthly period, no new purchases, no fees, and no missed payments. Actual lenders may use daily balances, different billing-cycle lengths, cent-by-cent rounding, or minimum-payment formulas that add interest and fees to a principal percentage. The fixed comparison plan models the entered payment rather than enforcing a lender's contractual minimum. Payments that do not exceed monthly interest may prevent payoff; a finite payoff estimate is not meaningful when the modeled debt does not decline. Final payments can be smaller than the scheduled amount.
Common questions
Why does the 3% minimum plan take much longer than paying $200 each month?+
With the default $5,000 balance and 24% annual rate, the first month's modeled interest is $100 and the percentage minimum is $150, leaving only $50 to reduce principal. The $200 fixed payment reduces principal by $100 that month. As the minimum-plan balance falls, its percentage payment also falls, slowing repayment until the $35 floor applies.
Does the 3% minimum include interest, or is interest added to the payment?+
In this calculator, 3% of the starting monthly balance is the total scheduled payment before applying the $35 floor. Interest is charged to the balance, not added as a separate component of the minimum-payment formula. A lender that charges a principal percentage plus interest uses a different formula.
What happens when the percentage payment falls below $35?+
The minimum plan switches to the $35 floor rather than continuing to shrink with the balance. If the balance plus that month's interest is less than $35, the final payment is reduced to that remaining amount.
Are the default interest totals the total amounts repaid?+
No. The $8,441.75 minimum-plan interest and $2,000.56 fixed-plan interest exclude the original $5,000 balance. Including principal, total repayments are $13,441.75 and $7,000.56, respectively.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.