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Calculator results are estimates for planning, not a loan approval, commitment, rate lock, or Loan Estimate.
What the extra payment calculator calculates
This tool shows what happens when you add a fixed extra amount to your regular principal-and-interest payment every month: how much sooner the loan pays off, and how much total interest you avoid paying over the life of the loan.
Extra payments go entirely toward principal (assuming your servicer applies them that way — confirm this with your loan servicer, since some require you to specify 'apply to principal'), which reduces the balance interest is calculated on for every remaining payment, compounding the savings over time.
The earlier in the loan you start adding extra principal, the bigger the interest savings, because more of the loan's remaining term — and remaining interest — is still ahead of you.
How to use it, step by step
- 1Enter your current loan balance and interest rate.
- 2Enter your remaining term — how many years are left on the loan, not the original term.
- 3Enter an extra monthly principal amount you're considering adding — even a modest, consistent amount can make a meaningful difference.
- 4Review the new payoff timeline and compare it to your current remaining term.
- 5Review the estimated interest saved, and adjust the extra-payment amount to see how sensitive the savings are to different amounts.
A worked example
Example inputs
- Current loan balance
- $280,000
- Interest rate (example only)
- 6.5%
- Remaining term
- 27 years
- Extra monthly principal
- $200
Result
Adding $200 a month in extra principal on this balance, at the illustrative 6.5% rate, shortens the remaining 27-year payoff timeline by roughly 5 years in this example.
Because each extra-principal dollar reduces the balance that future interest is calculated on, the total interest saved over the shortened term is typically well beyond the simple sum of the extra payments themselves — the compounding is what makes consistent extra payments powerful.
The 6.5% rate above is an illustrative example input only, not a current quote.
How to read the result
Compare the new payoff timeline against your current remaining term to see how many years an extra payment actually removes from the loan.
Interest saved is the clearest measure of the financial benefit — it captures the full compounding effect of paying down principal faster, not just the extra dollars themselves.
Confirm with your loan servicer that extra payments are being applied to principal, not just collected as an early payment toward next month's regular bill — the two produce very different results.
Common mistakes
- Sending extra money without confirming with the servicer that it's applied to principal — some servicers default to holding it toward the next scheduled payment unless you specify otherwise.
- Committing to a large extra payment that strains the monthly budget, when a smaller, sustainable amount kept up consistently often produces similar long-run savings.
- Ignoring a prepayment penalty clause, if one exists on the loan — most conventional mortgages don't have one, but it's worth confirming before committing to an aggressive extra-payment plan.
- Prioritizing extra mortgage principal over higher-interest debt (like credit cards) or before building a basic emergency fund, when those often deserve attention first.
Related guides
- 15-Year vs. 30-Year Calculator
- Refinance Break-Even Calculator
- Mortgage Payment Calculator
- Glossary: Interest Rate
Frequently asked questions
Not automatically in every case. Most servicers will apply a clearly marked extra payment to principal, but some default to holding it as a credit toward your next regular payment unless you specify 'apply to principal.' Always confirm directly with your servicer.
Extra payments keep the flexibility to stop if your budget changes, while a shorter-term refinance locks in a higher required payment (often at a lower rate) with less flexibility. Both can produce similar interest savings — the right choice depends on how much payment flexibility you want.
Yes — extra payments made earlier in the loan save more total interest than the same extra payments made later, because more principal and remaining term are still ahead of you early on.
Most conventional mortgages issued today don't carry prepayment penalties, but some loan types and older loans can. Check your loan documents or ask your servicer before committing to an aggressive extra-payment plan.
It depends on your mortgage rate, your other debts, your risk tolerance, and your overall financial picture. There's no universal answer — some homeowners prioritize the guaranteed, risk-free return of paying down a mortgage; others prioritize long-term investing. Consider talking with a financial advisor about your specific situation.