Amortization Calculator

Written by Great Medico

Updated September 25, 2026 •3 min read

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A finance number becomes easier to trust when you can trace it back to the inputs. Amortization Calculator calculates the scheduled payment for an amortizing loan from principal, rate, term, payment frequency, fees, and any extra-payment amount shown.

What this calculator does

Amortization Calculator calculates the scheduled payment for an amortizing loan from principal, rate, term, payment frequency, fees, and any extra-payment amount shown. The form asks for loan amount, annual interest rate, loan term, payment frequency, upfront loan/origination fees, and extra payment each period. The result should therefore be read as a calculation from those displayed assumptions, not as live market, lender, tax, or government-program data unless the page explicitly supplies such a feed.

How to use it

Enter Loan amount, Annual interest rate, Loan term, Payment frequency, Upfront loan/origination fees, and Extra payment each period. Keep monetary inputs in one currency; the currency selector formats results and does not convert exchange rates. Enter rates and percentages on the scale shown by the field label; do not silently switch between a decimal and a percent. Keep time values in the period shown on the form so a monthly figure is not accidentally entered as an annual one or vice versa. Before calculating, recheck Loan amount, Annual interest rate, Loan term against the source values you intend to model. If a default value is already filled in, confirm that it matches the scenario you actually want to test rather than assuming the preset is current or personally appropriate.

How the calculation works

Scheduled payment follows the standard annuity formula using the entered principal plus financed fees. Total scheduled repayment equals payment × number of payments; total interest is scheduled repayment minus the borrowed principal before any separate extra-payment effect. This is the calculation method to use when checking the result from Amortization Calculator; values not represented by a visible input should not be inferred as part of the model.

Example

Use a small test case with the same types of inputs shown on Amortization Calculator, calculate the main relationship by hand, and compare it with the displayed result. Once that check makes sense, replace the sample values with your real scenario.

How to interpret the result

A higher rate or larger balance raises the scheduled payment. More frequent or extra payments can alter payoff timing, but the headline payment should be read together with the payment count and total-interest estimate. The result is most informative when you also look at the component values that drove it.

Limitations and notes

This is a mathematical amortization model. Daily interest, irregular payment dates, lender fees, late charges, escrow, payment holidays, rounding, and contract-specific application of extra payments can produce different statements. Recalculate when rates, balances, prices, dates, or policy rules change.