Mortgage Payoff Calculator
See what sending extra money toward principal each month does to your payoff date and the interest you avoid.
What this calculator does
This mortgage payoff calculator shows what happens when you send extra money toward principal. Enter your current balance, your interest rate, the years remaining, and the extra amount you plan to add each month, and it returns the interest you avoid and how many months earlier the loan disappears.
The table runs the two schedules in parallel — the standard balance and the accelerated one — with the widening gap between them in a third column. Watching that gap grow makes the mechanism obvious: every dollar of principal you remove today cancels every future dollar of interest that balance would have generated, which is why the saving is so much larger than the extra you pay in.
When to use it
Reach for it when you have surplus cash and are choosing where it goes: a raise, a bonus, the month a car loan finishes, or an inheritance. The interest-saved figure gives you a concrete return to compare against investing the same money.
It is also the tool for a specific deadline. If you want the mortgage gone before a child starts college or before you retire, work backward — try extra amounts until the months-saved figure lands on the date you need, then check that payment fits your budget. And it settles the question of whether to refinance for a shorter term: overpaying a 30-year loan to a 20-year schedule costs nothing in closing fees and can be stopped any month you need the cash back.
Understanding the inputs
Current balance is the payoff figure from your latest statement, not the original loan amount and not the amount you borrowed minus payments made. Interest rate is your note rate. Remaining term is the years left on the current schedule — if you took a 30-year loan eight years ago, that is 22, not 30.
Extra monthly payment is where the experimentation happens. It is worth testing small amounts, because the relationship is not linear: the first $100 saves proportionally more than the fifth $100, since it comes off while the balance is largest. Also try the equivalent of one extra payment spread across the year, which is roughly one twelfth of your monthly payment.
How is this calculated?
Calculate standard payoff date, then recalculate with extra principal applied monthly to determine new payoff date and interest saved.
A worked example
Take a $285,000 balance at 6.25 percent with 22 years remaining. The required payment is about $1,989 a month, and if you simply run the schedule out you will pay roughly $240,100 in interest before it clears.
Add $300 a month. The payment becomes $2,289, the loan clears in 202 months instead of 264 — five years and two months early — and total interest falls to about $175,700. That is roughly $64,400 saved for $300 a month over about seventeen years, a total outlay of around $60,600 in extra principal. Put differently, every extra dollar you send removes slightly more than a dollar of future interest, and it does so risk-free.
Limitations and assumptions
The model assumes each extra payment reaches principal immediately and that your rate never changes. It does not include escrow for taxes and insurance, so the payment shown is smaller than what leaves your account, and it does not model PMI dropping off as your balance falls — which is a real additional saving from overpaying if you are above 80 percent LTV.
It also cannot weigh the alternatives for you. Employer 401(k) matching is an instant fifty or hundred percent return that no mortgage rate beats, and high-interest consumer debt costs far more than a mortgage. Confirm with your servicer that extra payments are applied to principal on receipt, keep your emergency fund intact, and treat the interest-saved figure as the return you are comparing against everything else you could do with the money.
Common Questions
- Does an extra payment go straight to principal?
- Only if you tell the servicer. Many will otherwise hold the money as a partial next payment or apply it as a prepaid installment, which does nothing for your interest. Send extra funds separately from the regular payment and mark them "apply to principal" — most online portals now have a dedicated field for it.
- Is it better to pay extra or invest the money?
- Paying down a 6.5 percent mortgage is a guaranteed 6.5 percent return with no volatility and no tax on the gain. Equities have historically beaten that, but not reliably over any given ten-year stretch. If your rate is under four percent the investing case is strong; above six percent it gets much weaker.
- Should I clear other debt first?
- Almost always. Credit card interest at 22 percent and personal loans in the double digits cost far more than a mortgage, and unlike a mortgage the interest is never deductible. Extra principal payments only make sense once nothing higher-rate is outstanding and you have an emergency fund in place.
- Will overpaying lower my monthly payment?
- No. Extra principal shortens the term instead — the required payment stays the same and the loan simply ends sooner. If you want a lower monthly payment you need a recast, where the servicer re-amortizes the reduced balance over the remaining term, usually after a lump sum and for a fee of a few hundred dollars.
- Are there prepayment penalties?
- Rare on modern owner-occupied loans. Qualified mortgages restrict them heavily and they are banned outright on FHA and VA loans. They still appear on some non-QM, investor, and hard-money products, typically as a percentage of the balance in the first three years. Check your note before making large payments.
- Does paying extra hurt my mortgage interest deduction?
- Only if you itemize, and roughly nine in ten filers no longer do. Even for itemizers the deduction returns your marginal rate on the interest — you still lose the other 60 to 76 cents of every dollar. Never pay interest to save tax.
- Is a lump sum or monthly extra better?
- Whichever arrives sooner. Interest accrues on the balance, so a dollar applied today removes more future interest than the same dollar applied next year. A $10,000 lump sum now typically beats $200 a month for four years, even though the totals are similar.
- Should I keep an emergency fund instead?
- Yes, first. Money paid into a mortgage is very hard to get back out — you would need a cash-out refinance or a HELOC, both of which require qualifying, take weeks, and cost money. Three to six months of expenses in cash should be in place before you accelerate payoff.
- How much time does one extra payment a year save?
- On a 30-year loan at typical rates, one additional monthly payment each year usually cuts around four to five years off the term. The effect is largest early, when almost the entire payment would otherwise be interest, and shrinks considerably in the final decade.
Related calculators
- Bi-Weekly Mortgage Payment CalculatorCompare a standard monthly schedule against paying half your payment every two weeks, and see the interest and years it saves.
- Mortgage Points CalculatorFind out whether buying discount points makes financial sense by calculating your break-even period and long-term interest savings.
- Mortgage Refinance CalculatorCompare your existing mortgage against a proposed new one, including closing costs, and find the point at which the switch pays for itself.