Extra Mortgage Payment Calculator
See how extra mortgage payments reduce interest and accelerate your payoff date. Add extra monthly, annual, or one-time lump-sum payments to your standard amortization.
Formulas, assumptions, and rounding are documented in our calculator methodology.
Extra Payments (optional)
Base Monthly Payment
$1,896.20
Loan Payoff Comparison
- Standard payoff term
- 30 yrs
- Payoff term
- 30 yrs
- Time saved
- 0 yrs
Interest Comparison
- Total interest (standard)
- $382,633
- Total interest (with extras)
- $382,633
- Interest saved
- $0
How Extra Payments Reduce Interest
Every extra dollar applied to mortgage principal reduces the balance on which future interest is calculated. On a $300,000 loan at 6.5%, the first monthly payment is about $1,896 — of which roughly $1,625 is interest and only $271 is principal. Extra payments skip ahead in the amortization schedule, eliminating future high-interest months from the end of the loan.
Monthly vs. Annual vs. Lump-Sum Extra Payments
Monthly extra payments provide steady amortization acceleration and compound throughout the year. Annual extra payments (such as year-end bonuses or tax refunds) offer flexibility without committing to higher recurring payments. A single lump-sum payment, especially in the first few years, can dramatically shorten the loan. This calculator allows you to model all three simultaneously.
Bi-Weekly Payment Strategy
A common extra-payment strategy is switching to bi-weekly payments (half your monthly payment every two weeks). Because there are 26 bi-weekly periods per year, this results in 13 full monthly payments instead of 12 — effectively one extra payment per year. On a 30-year $300,000 loan at 6.5%, this strategy typically saves 4–5 years and tens of thousands in interest.
Frequently Asked Questions
- On a $300,000 mortgage at 6.5%, an extra $100/month saves approximately $37,000 in interest and shortens the loan by about 4 years. The exact impact depends on your loan balance, rate, and remaining term.
- Yes — higher interest rates make extra payments more valuable because more of each payment is going to interest. At 7%, extra payments save more than at 4% for the same extra dollar amount.
- This depends on your mortgage rate vs. expected investment return, tax situation, and risk tolerance. If your mortgage rate is 7% and you expect investment returns of 10%, investing may generate more wealth — but mortgage payoff is guaranteed and risk-free. Many people benefit from doing both.
- Contact your lender to confirm how to designate a payment as 'principal only.' Some lenders apply extra payments to future payments by default rather than to principal — make sure to specify your intent to avoid this.
- Yes. A single lump-sum payment early in the loan can save tens of thousands in interest. Because early payments reduce the principal on which all future interest is calculated, paying down principal in the first few years has the highest leverage.