CalcLibrary

Debt Payoff Calculator

Estimate how long it could take to pay off a debt and how extra payments may reduce interest and shorten the payoff timeline.

Examples

Credit Card Debt — $15,000

A $15,000 credit card balance at 18.9% APR with $300 minimum payment.

Current Balance
$15,000
Annual Interest Rate
18.9 %
Minimum Monthly Payment
$300
Extra Monthly Payment
$0
Months to Payoff
100 months
Total Interest Paid
$14,733.15
Total Amount Paid
$29,733.15
Months Saved vs. Minimum Only
0 months
Status
On track

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How It Works

Formula

It=Bt−1×r12I_t = B_{t-1} \times \frac{r}{12}

Bt=Bt−1+It−PtB_t = B_{t-1} + I_t - P_t

Variables, symbols and units

BtB_t

Balance at end of month t

Bt−1B_{t-1}

Balance at end of the previous month

ItI_t

Interest accrued in month t

PtP_t

Payment made in month t (minimum + extra)

rr

Annual interest rate (decimal)
Calculation method explained

Enter your current debt balance, annual interest rate, minimum monthly payment, and any extra payment you can make. The calculator simulates the month-by-month payoff, showing how long it takes, how much total interest you will pay, and how many months you save with extra payments compared to minimums only.

Month-by-month simulation, repeated until the balance reaches zero:

  1. Accrue interest on the previous balance: It=Bt−1×r/12I_t = B_{t-1} \times r/12.
  2. Apply the payment, capped so it never exceeds what is owed: Pt=min⁡(Minimum+Extra,  Bt−1+It)P_t = \min(\text{Minimum} + \text{Extra},\; B_{t-1} + I_t).
  3. Update the balance: Bt=Bt−1+It−PtB_t = B_{t-1} + I_t - P_t.
  4. Repeat until Bt=0B_t = 0.

Months saved is the difference between the minimum-only run and the run with extra payments. If the payment never exceeds the monthly interest, the balance grows and the calculator reports that the debt cannot be paid off under those terms.

References and source material

Examples

Credit Card Debt — $15,000$15,000 · 18.9 % → 100 months

A $15,000 credit card balance at 18.9% APR with $300 minimum payment.

Current Balance
$15,000
Annual Interest Rate
18.9 %
Minimum Monthly Payment
$300
Extra Monthly Payment
$0
Months to Payoff
100 months
Credit Card with Extra $200/month$15,000 · 18.9 % → 41 months

Same $15,000 balance but with $200 extra per month — see the savings.

Current Balance
$15,000
Annual Interest Rate
18.9 %
Minimum Monthly Payment
$300
Extra Monthly Payment
$200
Months to Payoff
41 months
Personal Loan — $8,000$8,000 · 10.5 % → 31 months

An $8,000 personal loan at 10.5% with $250/month payments plus $50 extra.

Current Balance
$8,000
Annual Interest Rate
10.5 %
Minimum Monthly Payment
$250
Extra Monthly Payment
$50
Months to Payoff
31 months

Frequently Asked Questions

How are the interest savings calculated?
The calculator simulates your payoff month by month. Each month, interest accrues on the remaining balance, your payment reduces the balance, and the process repeats. With extra payments, the balance drops faster so less interest accumulates. The savings are the difference between the two scenarios.
What if my minimum payment doesn't cover the monthly interest?
If your payment does not cover the monthly interest, the balance can grow instead of shrink. This is called negative amortization. The calculator marks that case as not payable under the current terms.
Should I pay extra on my debt or invest instead?
Paying down high-interest debt can improve your financial foundation because the interest you avoid may exceed returns available from many investments. This calculator does not decide for you; it only shows the debt-payoff side of that tradeoff.
What is the avalanche vs. snowball method?
The highest-interest-rate method puts extra payments toward the most expensive debt first. The snowball method puts them toward the smallest balance first. CFPB notes the highest-interest-rate method can eliminate the most costly debt first, while the snowball method can create quicker progress and motivation for some people.
Does this calculator handle multiple debts?
This calculator models one debt at a time. For multiple debts, run each balance separately. If you use the highest-interest-rate method, direct extra payments to the highest-rate debt first; if you use a snowball plan, focus on the smallest balance first.

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