Financial

Amortization Calculator

Build a fast payoff summary with first-payment detail and extra-payment impact.

Inputs

Defaults are prefilled so the result is visible immediately.

Loan amount

Interest rate%

Termyears

Extra monthly payment

Results

Results update as the calculator inputs change.

Monthly payment

$1,970.30

Total interest

$389,306.21

Payoff with extra

315 months

Interest saved

$57,726.33

First interest charge

$1,666.67

First principal paid

$303.63

Formula and Assumptions

Each month interest equals balance x monthly rate; the rest of the payment reduces principal.

The first-payment split helps explain why early payments are interest-heavy.

Extra principal is modeled as recurring and can shorten the payoff date.

Reference Upgrade

Built from the Calculator.net model, with added context.

Live validation and instant result updates instead of a submit-only workflow.

Multiple decision metrics are shown together, not only the primary answer.

Formula notes and assumptions are visible on the page so the math is easier to audit.

Reference Model

Modeled after the input style and primary output on Calculator.net's Amortization Calculator.

The page keeps the math in one place and exposes the assumptions beside the result.

Default inputs: loanAmount=320000, interestRate=6.25, termYears=30, extraPayment=100