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Extra payment calculator (how much you save)

See how many months and how much interest you save by paying extra on your loan every month.

$
%/mo
$
$
Interest saved
$73,500.00
Time saved39 months (3.3 yrs)
Payoff without extra165 months
Payoff with extra126 months

Fixed-payment estimate, with the extra reducing the balance monthly. With insured loans, the real saving tends to be even bigger.

Interactive lesson: Where your loan payment goes See what a $300k mortgage really costs, compare both amortization systems, and why your first payment is almost all interest. Glossary · MoneyMojisWhat amortization is, and why extra payments cut interest.

How the calculation works

Every extra unit goes straight to the principal — and stops generating interest for all remaining months. We compute the payoff time with and without the extra (n = −log(1 − S·i/P) ÷ log(1+i)) and compare totals.

Examples

  • Balance R$300k at 0.9%/mo, payment R$3,500: R$500 extra/mo pays off ~39 months sooner and saves ~R$73k in interest.
  • One large early prepayment saves far more interest than the same amount paid near the end.

Frequently asked questions

Shorten the term or lower the payment?

Shortening the term saves far more interest — the payment stays the same and the debt ends sooner. Lowering the payment eases the month but keeps interest running longer.

Pay extra or invest the money?

Compare rates: if the loan charges more than your investments earn (after tax), paying extra is a higher guaranteed return.

Why does paying early save more?

Because early on most of the payment is interest on a large balance. Every unit cut early avoids interest for many months.

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Updated on July 5, 2026 · by Rafael Rossi · Methodology & sources