Mortgage Prepayment Calculator
Estimate how extra principal payments can reduce your loan term and save interest.
How a mortgage prepayment calculator helps
A mortgage prepayment calculator shows the financial impact of sending extra money toward principal. Even small recurring prepayments can reduce total interest and shorten the payoff timeline. This tool is useful whether you're planning monthly extra payments, a yearly bonus payment, or a one-time lump sum.
What this calculator estimates
- Your estimated regular monthly mortgage payment (principal + interest)
- Total interest paid with no prepayment
- Payoff timeline with extra principal payments
- Interest saved and time saved from your prepayment strategy
- A quick first-year amortization preview with prepayment included
Input guide
Original loan amount
This is the starting principal balance of your mortgage. If you are already years into your loan, you can still use this calculator as a planning model, but for highest accuracy use your current balance and remaining term in a dedicated remaining-balance calculator.
Interest rate and term
Enter your annual fixed interest rate and loan term in years (for example, 30 or 15). The calculator applies standard amortization math to produce your baseline monthly payment and compares that against a prepayment scenario.
Extra monthly prepayment
Add a recurring amount you can pay every month. This is one of the most effective ways to accelerate mortgage payoff because every extra dollar reduces principal immediately, lowering future interest charges.
One-time lump sum
If you expect a tax refund, bonus, inheritance, or equity sale, you can simulate a one-time principal reduction in a specific month. This can produce a noticeable drop in total interest paid.
Practical mortgage prepayment strategies
- Round up your payment: If your payment is $2,213, consider paying $2,300.
- Biweekly equivalent: Make half your payment every two weeks to simulate one extra annual payment.
- Commit windfalls: Use bonuses and refunds to make lump-sum principal payments.
- Automate extra principal: Set an auto-transfer so your strategy happens consistently.
When prepaying may not be your top priority
Mortgage prepayment is usually beneficial, but not always the first move. If you carry high-interest debt, lack an emergency fund, or miss retirement matching contributions, those priorities may provide better financial returns. A balanced plan often works best: protect liquidity, eliminate expensive debt, then accelerate mortgage payoff.
Frequently asked questions
Does prepayment reduce my monthly required payment?
In most standard mortgages, no. Your required payment stays the same, but your loan ends earlier. Some lenders offer recasting after a large prepayment, which can lower required monthly payments.
Should I prepay or invest?
It depends on your risk tolerance, expected investment returns, and mortgage rate. Paying down your mortgage provides a guaranteed return equal to your loan rate (before taxes), while investing can offer higher potential returns with market risk.
Do I need to specify principal-only payment?
Yes. When sending extra money, confirm with your lender that additional funds are applied to principal, not future scheduled payments.
Educational use only. Estimates are simplified and do not include taxes, insurance, HOA dues, or lender-specific fees.