Debt Payoff Calculator
Calculate how long it takes to pay off a debt and the total interest, given a fixed monthly payment.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
Breakdown
About this calculator
This is a simplified payoff estimate for one balance at a constant average APR, with a fixed monthly payment and no new charges or fees. Actual debts may have different rates, fees and payment timing.
Worked example
calculated with the default values below
Total debt balance 15,000 $ · Average annual interest rate 18 % · Monthly payment 400 $ Months to clear 56 months · Years to clear 4.67 years · Total interest paid 7,210.43 $ · Total paid 22,210.43 $
Method and assumptions
i = APR ÷ 1200; B_{k+1} = B_k(1 + i) − P Iterate from B₀ = total debt until B_k ≤ 0.01 (max 1200 months). If P ≤ B_k×i the balance never falls — payment too small; totals accumulate interest and amounts paid. This is a simplified payoff estimate for one balance at a constant average APR, with a fixed monthly payment and no new charges or fees. Actual debts may have different rates, fees and payment timing.
Data sources
Disclaimer
These calculators give estimates for general information only. They are not financial, tax or investment advice and do not take your personal circumstances into account. Before borrowing, investing or filing, confirm the numbers with a qualified adviser in your jurisdiction.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
i = APR ÷ 1200; B_{k+1} = B_k(1 + i) − P
- APR
- Annual percentage rate
- i
- Monthly rate
- P
- Monthly payment
- B_k
- Balance in month k
- n
- Months to payoff
Iterate from B₀ = total debt until B_k ≤ 0.01 (max 1200 months). If P ≤ B_k×i the balance never falls — payment too small; totals accumulate interest and amounts paid.
Frequently asked questions
Why does the payoff calculator warn when payments are too low?
If a payment is no greater than modeled monthly interest (APR ÷ 12 × balance), the balance cannot shrink and the calculator reports a payment-too-low error. Otherwise it simulates monthly interest and a fixed payment for up to 1,200 months, assuming one balance, one average APR and no new charges or fees.
Which inputs and limits apply to Debt Payoff Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Total debt balance: 0–100,000,000 $; Average annual interest rate: 0–100 %; Monthly payment: 1–10,000,000 $ i = APR ÷ 1200; B_{k+1} = B_k(1 + i) − P Iterate from B₀ = total debt until B_k ≤ 0.01 (max 1200 months). If P ≤ B_k×i the balance never falls — payment too small; totals accumulate interest and amounts paid. This is a simplified payoff estimate for one balance at a constant average APR, with a fixed monthly payment and no new charges or fees. Actual debts may have different rates, fees and payment timing.
What is a complete worked example for Total debt balance = 15,000 $; Average annual interest rate = 18 %?
Inputs: Total debt balance = 15,000 $; Average annual interest rate = 18 %; Monthly payment = 400 $. Calculation: i = APR ÷ 1200; B_{k+1} = B_k(1 + i) − P. Results: Months to clear = 56 months; Years to clear = 4.67 years; Total interest paid = 7,210.43 $; Total paid = 22,210.43 $.