Loan Payoff Calculator

Project your loan payoff date, total interest, and savings from extra monthly payments or a one-time lump sum. See how faster payments shorten your timeline with a detailed amortization schedule.

Amortization schedule

Loan payoff schedule including extra payments and lump sum
# Payment Interest Principal Extra Balance
Enter loan details to generate the schedule.

Full original guide (expanded)

Loan Payoff Calculator

Find out how quickly you can become debt-free by adding extra monthly payments or a one-time lump sum. The calculator shows the new payoff date, interest saved, and a detailed amortization preview.

Author: Ugo Candido Reviewed by: Finance Content Editor Last updated: Category: Finance → Loans & Debt
$
%
$
$
$

Used to estimate the payoff month.

Results

Months to payoff 0 Scheduled without extras: 0
Estimated payoff date — Start: —
Total interest (with extras) $0.00 Interest saved vs. baseline: $0.00
Total interest (baseline) $0.00 No lump sum or extra payments
Lump sum applied $0.00
Extra monthly payment $0.00
Ready to calculate

Data Source and Methodology

Calculations follow standard amortization math used in Truth in Lending (Regulation Z) Appendix J. Monthly interest is computed as APR ÷ 12, and extra payments are applied directly to principal each period after deducting interest. Lump sums reduce the balance immediately before the first period of the simulation.

Formulas Used

Monthly rate: \( r = \frac{\text{APR}}{12} \)

Baseline payment check: If \( P_{\text{mt}} \leq B \cdot r \) the payment is too small and the balance grows.

Iteration:

  • Interest \( = B_{t-1} \cdot r \)
  • Principal \( = \min\big(P_{\text{mt}} + E - \text{Interest},\, B_{t-1}\big) \)
  • Balance \( = \max\big(B_{t-1} - \text{Principal},\, 0\big) \)

Total interest is the sum of interest across periods; the payoff month is reached when the balance becomes zero.

Worked Example

Balance $20,000, APR 6.5%, payment $450, extra $75/month, lump sum $1,000 today:

  1. Lump sum reduces balance to $19,000 before the first payment.
  2. Monthly interest initially ≈ $102.92; principal paid ≈ $422.08.
  3. With the extra $75, payoff occurs in ≈ 43 months instead of 51.
  4. Total interest drops from ≈ $3,148 to ≈ $2,589, saving ≈ $559.

Negative Amortization Warning

If your monthly payment is less than the monthly interest, the loan balance increases. The calculator flags this condition and asks for a higher payment or additional lump sum to guarantee payoff.

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\\]
','\
Formula (extracted text)
Monthly rate: \( r = \frac{\text{APR}}{12} \) Baseline payment check: If \( P_{\text{mt}} \leq B \cdot r \) the payment is too small and the balance grows. Iteration: Interest \( = B_{t-1} \cdot r \) Principal \( = \min\big(P_{\text{mt}} + E - \text{Interest},\, B_{t-1}\big) \) Balance \( = \max\big(B_{t-1} - \text{Principal},\, 0\big) \) Total interest is the sum of interest across periods; the payoff month is reached when the balance becomes zero.
Variables and units
  • P = principal (loan amount) (currency)
  • r = periodic interest rate (annual rate ÷ payments per year) (1)
  • n = total number of payments (years × payments per year) (count)
  • M = periodic payment for principal + interest (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

Need more help?

Explore more tools in the Loans & Debt hub or visit the Personal loans center for budgeting and payoff strategies.

Loan Payoff Calculator

Find out how quickly you can become debt-free by adding extra monthly payments or a one-time lump sum. The calculator shows the new payoff date, interest saved, and a detailed amortization preview.

Author: Ugo Candido Reviewed by: Finance Content Editor Last updated: Category: Finance → Loans & Debt
$
%
$
$
$

Used to estimate the payoff month.

Results

Months to payoff 0 Scheduled without extras: 0
Estimated payoff date — Start: —
Total interest (with extras) $0.00 Interest saved vs. baseline: $0.00
Total interest (baseline) $0.00 No lump sum or extra payments
Lump sum applied $0.00
Extra monthly payment $0.00
Ready to calculate

Amortization schedule

Loan payoff schedule including extra payments and lump sum
# Payment Interest Principal Extra Balance
Enter loan details to generate the schedule.

Data Source and Methodology

Calculations follow standard amortization math used in Truth in Lending (Regulation Z) Appendix J. Monthly interest is computed as APR ÷ 12, and extra payments are applied directly to principal each period after deducting interest. Lump sums reduce the balance immediately before the first period of the simulation.

Formulas Used

Monthly rate: \( r = \frac{\text{APR}}{12} \)

Baseline payment check: If \( P_{\text{mt}} \leq B \cdot r \) the payment is too small and the balance grows.

Iteration:

  • Interest \( = B_{t-1} \cdot r \)
  • Principal \( = \min\big(P_{\text{mt}} + E - \text{Interest},\, B_{t-1}\big) \)
  • Balance \( = \max\big(B_{t-1} - \text{Principal},\, 0\big) \)

Total interest is the sum of interest across periods; the payoff month is reached when the balance becomes zero.

Worked Example

Balance $20,000, APR 6.5%, payment $450, extra $75/month, lump sum $1,000 today:

  1. Lump sum reduces balance to $19,000 before the first payment.
  2. Monthly interest initially ≈ $102.92; principal paid ≈ $422.08.
  3. With the extra $75, payoff occurs in ≈ 43 months instead of 51.
  4. Total interest drops from ≈ $3,148 to ≈ $2,589, saving ≈ $559.

Negative Amortization Warning

If your monthly payment is less than the monthly interest, the loan balance increases. The calculator flags this condition and asks for a higher payment or additional lump sum to guarantee payoff.

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\\]
','\
Formula (extracted text)
Monthly rate: \( r = \frac{\text{APR}}{12} \) Baseline payment check: If \( P_{\text{mt}} \leq B \cdot r \) the payment is too small and the balance grows. Iteration: Interest \( = B_{t-1} \cdot r \) Principal \( = \min\big(P_{\text{mt}} + E - \text{Interest},\, B_{t-1}\big) \) Balance \( = \max\big(B_{t-1} - \text{Principal},\, 0\big) \) Total interest is the sum of interest across periods; the payoff month is reached when the balance becomes zero.
Variables and units
  • P = principal (loan amount) (currency)
  • r = periodic interest rate (annual rate ÷ payments per year) (1)
  • n = total number of payments (years × payments per year) (count)
  • M = periodic payment for principal + interest (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

Need more help?

Explore more tools in the Loans & Debt hub or visit the Personal loans center for budgeting and payoff strategies.

Loan Payoff Calculator

Find out how quickly you can become debt-free by adding extra monthly payments or a one-time lump sum. The calculator shows the new payoff date, interest saved, and a detailed amortization preview.

Author: Ugo Candido Reviewed by: Finance Content Editor Last updated: Category: Finance → Loans & Debt
$
%
$
$
$

Used to estimate the payoff month.

Results

Months to payoff 0 Scheduled without extras: 0
Estimated payoff date — Start: —
Total interest (with extras) $0.00 Interest saved vs. baseline: $0.00
Total interest (baseline) $0.00 No lump sum or extra payments
Lump sum applied $0.00
Extra monthly payment $0.00
Ready to calculate

Amortization schedule

Loan payoff schedule including extra payments and lump sum
# Payment Interest Principal Extra Balance
Enter loan details to generate the schedule.

Data Source and Methodology

Calculations follow standard amortization math used in Truth in Lending (Regulation Z) Appendix J. Monthly interest is computed as APR ÷ 12, and extra payments are applied directly to principal each period after deducting interest. Lump sums reduce the balance immediately before the first period of the simulation.

Formulas Used

Monthly rate: \( r = \frac{\text{APR}}{12} \)

Baseline payment check: If \( P_{\text{mt}} \leq B \cdot r \) the payment is too small and the balance grows.

Iteration:

  • Interest \( = B_{t-1} \cdot r \)
  • Principal \( = \min\big(P_{\text{mt}} + E - \text{Interest},\, B_{t-1}\big) \)
  • Balance \( = \max\big(B_{t-1} - \text{Principal},\, 0\big) \)

Total interest is the sum of interest across periods; the payoff month is reached when the balance becomes zero.

Worked Example

Balance $20,000, APR 6.5%, payment $450, extra $75/month, lump sum $1,000 today:

  1. Lump sum reduces balance to $19,000 before the first payment.
  2. Monthly interest initially ≈ $102.92; principal paid ≈ $422.08.
  3. With the extra $75, payoff occurs in ≈ 43 months instead of 51.
  4. Total interest drops from ≈ $3,148 to ≈ $2,589, saving ≈ $559.

Negative Amortization Warning

If your monthly payment is less than the monthly interest, the loan balance increases. The calculator flags this condition and asks for a higher payment or additional lump sum to guarantee payoff.

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\\]
','\
Formula (extracted text)
Monthly rate: \( r = \frac{\text{APR}}{12} \) Baseline payment check: If \( P_{\text{mt}} \leq B \cdot r \) the payment is too small and the balance grows. Iteration: Interest \( = B_{t-1} \cdot r \) Principal \( = \min\big(P_{\text{mt}} + E - \text{Interest},\, B_{t-1}\big) \) Balance \( = \max\big(B_{t-1} - \text{Principal},\, 0\big) \) Total interest is the sum of interest across periods; the payoff month is reached when the balance becomes zero.
Variables and units
  • P = principal (loan amount) (currency)
  • r = periodic interest rate (annual rate ÷ payments per year) (1)
  • n = total number of payments (years × payments per year) (count)
  • M = periodic payment for principal + interest (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

Need more help?

Explore more tools in the Loans & Debt hub or visit the Personal loans center for budgeting and payoff strategies.

Formulas

(Formulas preserved from original page content, if present.)

Version 1.5.0
Citations

Add authoritative sources relevant to this calculator (standards bodies, manuals, official docs).

Changelog
  • 0.1.0-draft — 2026-01-19: Initial draft (review required).