Finance

Debt Payoff Calculator

Estimate how long it will take to pay off a single debt balance given the rate and a fixed monthly payment.

Last reviewed: April 30, 2026Free toolMethodology

Debt Payoff Calculator

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These fields start with sample inputs. Keep them or replace them, then run the tool to show a fresh result.

Number fields accept plain values and common formatted input such as 250000, 250,000, or 1,234.56.

Result

Calculating the sample result.

Why it matters

Payoff timelines can change dramatically based on payment size, which makes this one of the most practical debt-planning tools.

When to use

  • Comparing minimum payments against accelerated payments
  • Checking if a payment level is enough to cover interest and reduce principal
  • Planning a realistic payoff horizon for one balance

Inputs & Outputs

Inputs

  • Balance is the current debt principal.
  • Annual interest rate is the borrowing rate applied to the balance.
  • Monthly payment is the amount you plan to pay every month.

Outputs

  • Months to payoff estimates how long it takes to reach zero balance.
  • Total interest shows the financing cost over that period.

Payoff period method

The calculator solves for the number of payment periods required for a declining-interest balance to reach zero under a fixed monthly payment.

n = -ln(1 - (balance x monthly rate / payment)) / ln(1 + monthly rate)

Worked example

1

Accelerated payoff check

A 15,000 balance at 18% APR is paid down at 450 per month.

Inputs

  • Balance: 15,000
  • APR: 18%
  • Monthly payment: 450

Steps

  • Convert APR to monthly rate
  • Solve for the number of months required to amortize the balance

Result

  • The calculator shows the payoff horizon and total interest at the chosen payment level.

Edge cases & caveats

  • If the payment is too low to cover monthly interest, the balance will not amortize.
  • Fees and new charges are not included.

Frequently Asked Questions

Why does a small payment increase shorten the payoff period so much?

Because extra payment goes mostly to principal, which also reduces future interest charges.

Can I use this for installment loans and credit cards?

Yes, as long as you model a single balance and a steady payment amount.

Keep going

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