Loan Payoff Calculator

See the impact of extra payments on your loan payoff timeline and total interest.

Scratchpad (not saved)

Save to create a persistent, shareable workspace.

What This Calculator Does

Measure the time and interest savings created by additional loan payments beyond the scheduled minimum.

It combines Current Balance, Interest Rate, Current Monthly Payment, Extra Monthly Payment to estimate Interest Saved, Original Payoff, Original Total Interest.

Formula & Method

Core equations: Each month, interest accrues as:

I = B \times r

where

B

is the remaining balance and

r

is the monthly rate. Principal paid is

P = M - I

where

M

is the monthly payment. Extra payments and lump sums reduce

B

directly, saving interest over the life of the loan. Inputs are applied in base units, then derived metrics are computed from the same equations and rounded for display.

Notation used in the formulas: $R$ = Interest Saved; $x_{1}$ = Current Balance; $x_{2}$ = Interest Rate; $x_{3}$ = Current Monthly Payment; $x_{4}$ = Extra Monthly Payment; $x_{5}$ = One-Time Extra Payment.

Method summary: inputs are normalized to consistent units, core equations are evaluated, then secondary values are derived and rounded for display.

Use this when prioritizing debt reduction strategies and deciding where extra monthly cash has the largest impact.

Reference Book

Mathematics of Investment and Credit

Samuel A. Broverman · ACTEX Learning

A widely used text for time-value-of-money, annuity, loan, amortization, and bond calculations.

View Book

Inputs Used

Current Balance: Remaining loan balance
Interest Rate: Annual interest rate
Current Monthly Payment: Your current monthly payment amount
Extra Monthly Payment: Additional amount to pay each month
One-Time Extra Payment: A single lump-sum extra payment now

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