How Loan Prepayment Saves You Thousands in Interest
When you take a loan, each monthly payment is split between interest and principal. In the early years, the majority of every payment goes toward interest. On a 30-year mortgage of $300,000 at 6.5%, you end up paying roughly $382,000 in interest alone — more than the loan itself.
Every dollar you prepay goes directly to the principal. A smaller principal means every future month's interest is calculated on a smaller amount. This compounding effect is why even a modest extra payment of $200 per month can save tens of thousands and close your loan years earlier.
Shorten the Term, Not the Payment
When you prepay, your lender may ask: do you want a lower payment or a shorter term? Always choose the shorter term if you can afford the current payment. Shortening the term stops interest from accruing years earlier, which saves dramatically more money than a slightly lower monthly bill.
The Early Bird Advantage
Prepayment is most powerful in the first third of your loan. A $5,000 lump sum paid in year 2 can save 3-4x more interest than the same amount paid in year 15, simply because it eliminates many more months of interest on that principal.
Prepay vs Invest: The Simple Rule
Compare your loan's interest rate with the post-tax return you realistically expect from investing. If your mortgage charges 7% and your savings account earns 4% after tax, prepaying wins — it is a guaranteed, risk-free 7% return. Stocks may beat it long-term, but prepayment carries zero risk.
Check for Prepayment Penalties
Most modern mortgages have no prepayment penalty, but some fixed-rate loans, auto loans and personal loans charge 1-5% of the prepaid amount — factor that into your decision using this calculator.
How This Calculator Works
This tool rebuilds your complete amortization schedule month by month. It applies your extra monthly payment and any lump sum directly to the principal, then compares the total interest and payoff date against the original schedule. The math uses the standard reducing-balance method used by lenders worldwide.