Mortgage Payoff Accelerator

What this estimate assumes

• Your current monthly principal & interest payment is calculated from the standard fixed-rate amortization formula, using your remaining balance, rate, and remaining term — not what you're actually paying today, which may already include extra principal.
• The "extra needed" figure is the flat additional amount, on top of that calculated payment, added every month for the full payoff goal — real budgets fluctuate, so treat it as a target to aim for rather than an exact bill.
• This assumes every extra dollar goes straight to principal with no prepayment penalty — most home mortgages don't have one, but a small number of loans do, so it's worth checking your note.
• It doesn't account for refinancing into a shorter-term loan at a different rate, which is a separate way to get the same result and worth comparing with your lender.

How to use this calculator

1. Enter what you currently owe on the mortgage in Remaining loan balance ($) — check your most recent statement, not the original loan amount.
2. Enter your current rate in Interest rate (APR %).
3. Enter how many years are left on your current schedule in Remaining loan term (years).
4. Enter the number of years you'd like to be mortgage-free in Payoff goal (years) — for example, 15 if you want to turn a 30-year loan into a 15-year payoff.
5. Optionally, enter an amount you already know you can add every month in Extra you can actually add each month ($) to see what that specific amount actually gets you, instead of the amount required to hit your goal exactly.
6. Click See what it takes to see the extra monthly payment required, and how much interest it saves you.

Worked example

Take the calculator's own defaults: a $300,000 remaining balance at 6.5% APR, with 30 years left on the loan, and a goal of paying it off in 15 years instead.

At 6.5% over the full 30 remaining years, the standard amortization payment on $300,000 works out to about $1,896.18/month, which would cost roughly $382,625 in total interest before the loan is paid off. Run that same $300,000 balance through the amortization formula over just 180 months (15 years) instead, and the payment works out to about $2,615.04/month — roughly $718.86 more per month than the current payment — but total interest drops to about $170,707. That's an interest savings of roughly $211,918 for committing an extra $718.86 every month. The extra money isn't lost — it converts directly into equity and years of interest you never have to pay.

Frequently asked questions

Where do I find my "remaining loan balance" — is it the same as my original loan amount?

No — use your current payoff balance, not what you originally borrowed. You'll find it on your latest mortgage statement, usually labeled "principal balance" or "unpaid principal balance." Using the original loan amount will overstate both your current payment and the extra amount needed.

Does the extra payment actually need to be paid every single month to get this result?

Yes, for the "payoff goal" calculation — it assumes a consistent extra amount every month for the full target term. If your extra payments vary month to month, your actual payoff date will land somewhere close to, but not exactly at, the goal you entered.

Will my lender automatically apply extra payments to principal?

Not always automatically. Many servicers apply any amount above your scheduled payment to next month's payment first unless you specifically mark it "apply to principal." Check with your servicer and confirm how to designate extra payments — otherwise you may not get the payoff timeline this calculator shows.

Is paying extra toward my mortgage better than investing that money instead?

It depends on your mortgage rate versus what you'd realistically earn investing, plus how much you value a guaranteed, risk-free return. Paying down a 6.5% mortgage is a guaranteed 6.5% return on that money; this calculator only shows the mortgage side of that comparison, not investment projections.

Why does a relatively small extra payment save so much in interest?

Because interest is calculated on your remaining balance every month — extra principal paid today reduces the balance interest is charged on for every single month that follows, not just the current one. That compounding effect is why $718.86 extra a month can erase over $200,000 in future interest.

Does this account for prepayment penalties?

No — it assumes every extra dollar goes straight to principal with no penalty, which is true for the vast majority of U.S. mortgages originated in the last couple decades. A small number of older or non-conforming loans do carry prepayment penalties, so check your loan documents before committing to an extra-payment plan.