Two ways to apply one extra payment
The extra amount reduces principal after the number of regular payments you enter. Keep the original payment to finish earlier, or recast the remaining balance over the original remaining months to lower the payment. Results count interest from today forward.
Scheduled payment uses the current balance, rate, and remaining months
Each month: interest = balance × monthly rate, then principal is paid
After the chosen month, extra principal is subtracted
Net savings = interest avoided − prepayment fee
Each month: interest = balance × monthly rate, then principal is paid
After the chosen month, extra principal is subtracted
Net savings = interest avoided − prepayment fee
Example
A $250,000 balance at 6.5% with 300 months left, and $20,000 extra paid now, cuts later interest. Keeping the payment shortens the schedule; recasting over 300 months lowers the monthly amount. A $0 fee is the usual mortgage case.
What this schedule assumes
One extra payment, a fixed rate, and equal monthly amortizing payments. Biweekly plans, recurring extra amounts, interest-only periods, and daily interest are not modeled. Recasting the payment has to be allowed by the loan.