ToolSwoop.
Free online toolsFind a tool/
Calculators & Converters

Amortization Calculator

Build an amortization schedule and explore how a regular extra principal payment changes interest and payoff time while keeping the base payment fixed.

Free online tool

Loading tool…

Compare a standard amortization schedule with a fixed extra principal payment each month. The base payment stays fixed after extra payments; the final payment is reduced.

USD 1,073.64Base monthly payment
USD 1,173.64Payment including extra
62Months saved
USD 37,069.03Interest saved

Standard plan: 360 payments and USD 186,511.57 interest. With extra: 298 payments and USD 149,442.54 interest.

Balance trend from USD 200,000.00 to USD 0.00 over 298 periodsStartPeriod 298
Balance by period. The schedule provides exact period values.

Monthly schedule

Calculated at full precision; displayed amounts are rounded. CSV includes every period with six decimal places.

All amounts in USD
MonthOpeningInterest / growthPaymentClosing
1USD 200,000.00USD 833.33USD 1,173.64USD 199,659.69
2USD 199,659.69USD 831.92USD 1,173.64USD 199,317.96
3USD 199,317.96USD 830.49USD 1,173.64USD 198,974.81
4USD 198,974.81USD 829.06USD 1,173.64USD 198,630.23
5USD 198,630.23USD 827.63USD 1,173.64USD 198,284.21
6USD 198,284.21USD 826.18USD 1,173.64USD 197,936.75
7USD 197,936.75USD 824.74USD 1,173.64USD 197,587.85
8USD 197,587.85USD 823.28USD 1,173.64USD 197,237.49
9USD 197,237.49USD 821.82USD 1,173.64USD 196,885.66
10USD 196,885.66USD 820.36USD 1,173.64USD 196,532.38
11USD 196,532.38USD 818.88USD 1,173.64USD 196,177.62
12USD 196,177.62USD 817.41USD 1,173.64USD 195,821.38

Interest accrues before each month-end payment at annual rate ÷ 12. No prepayment penalties, recasting, escrow, taxes, or origination charges are modeled.

Your inputs and calculations stay in this browser. No live financial data is fetched; amounts use your selected USD or GBP labels.

GET STARTED

How to use the Amortization Calculator

  1. 01

    Enter the original loan principal, fixed nominal annual rate, and original term.

  2. 02

    Add the extra amount paid with every monthly payment.

  3. 03

    Compare payoff time and interest with the standard plan, then export the accelerated schedule.

Examples

Extra payments without interest

A 12,000 loan over 24 months at 0% has a 500 base payment. An extra 100 per month repays it in 20 months. The four-month time saving creates no interest saving because the rate is zero.

A small final payment

If the amount due is less than your usual base-plus-extra payment, only that remaining amount is paid. The schedule never creates a negative balance.

Two schedules, one starting point

The standard schedule uses the level payment needed to repay the original principal in the specified term. The accelerated schedule adds your extra amount after monthly interest is calculated. Both start with the same balance and interest rate, so the difference isolates the effect of extra payments.

Principal allocation and timing

Monthly interest equals opening principal multiplied by the annual nominal rate divided by 1,200. Payment minus interest reduces principal. Extra principal reduces later interest because less debt remains to accrue it. All payments occur at month end; no midmonth savings are assumed.

Payoff time versus payment size

This calculator shortens the repayment period while keeping the scheduled base payment unchanged. A loan recast that lowers later payments is a different scenario. The export includes opening balance, interest, actual payment, and closing balance for every simulated month.

What to know

  • No prepayment charges, payment holidays, recasting, variable rates, escrow, or daily accrual.
  • Calculations use full precision; account statements may round each period differently.

Common questions

Can I enter one lump-sum overpayment?

This form models the same extra payment every month. It does not support an isolated lump sum or an extra payment that starts later.

Does it account for prepayment penalties?

No. A penalty or charge can change the benefit of extra payments and must be considered separately from these interest-only arithmetic results.

Can I use a current remaining balance?

Yes, if you also supply the remaining term and want a newly calculated level payment. That may differ from your existing contractual payment.

Sources & references