The short answer
Last updated: July 2026
Adding extra principal to each mortgage payment shortens the loan and cuts total interest, because interest is charged on the remaining balance and a smaller balance accrues less. The saving is estimated by walking the amortization schedule with and without the extra payment and comparing. This assumes a fixed rate and every extra dollar going to principal.
After the estimate:
Self-management softwareMortgage payoff calculator
Pay a little extra. Finish years early.
Add extra principal to each monthly payment and see how much sooner the loan is paid off — and how much interest that saves over its life.
Current loan balance
$
Interest rate (APR)
6.50%
0%
12%
Years remaining
30 yrs
5 yrs
40 yrs
Extra principal per month
$
On top of the $2,023 scheduled principal & interest payment.
Input-driven result
Your inputs
Formula
Result below
Interest saved
$105,429
By adding $200/mo to the payment.
Time saved
6 yr 7 mo
Paid off in 23 yr 5 mo instead of 30 yr.
Payoff comparison
Scheduled interest
$408,142
Interest with extra
$302,714
Interest avoided
$105,429
Estimate based on your inputs. Not a promise of results.
Estimate only. It assumes a fixed rate and that every extra dollar goes to principal each month. It excludes taxes, insurance, and any prepayment terms — confirm your loan allows extra principal without a penalty.
Get early access
Watch it work
How it works
How this tool works.
A little extra on every mortgage payment goes entirely to principal, and because interest compounds on the balance, shrinking that balance early pays off out of proportion to the amount. Even a modest monthly add-on can knock years off a loan and save a striking amount of interest over its life.
Enter the loan balance, rate, and years remaining, plus the extra you’d pay each month, and this calculator estimates the time and interest saved. It simulates the amortization schedule month by month for both plans and compares them — an illustration from your inputs, not a prediction or an offer.
1
Enter the current loan balance, interest rate, and years remaining; the tool computes the scheduled monthly principal & interest.
2
Add the extra principal you’d pay each month on top of that scheduled payment.
3
The calculator walks the amortization schedule for both the baseline payment and the payment-plus-extra, month by month, until each is paid off.
4
It reports the interest saved and the time saved — estimates from your inputs, assuming a fixed rate and that every extra dollar goes to principal.
Make the result useful
Payoff speed has a cash-flow tradeoff
An extra principal payment can reduce interest and shorten the loan, but it also locks cash into equity. Compare the payoff benefit with the reserve you need for repairs, vacancy, and other obligations.
Apply only amounts confirmed as principal-only with your servicer; payment timing and loan terms affect the real schedule.
Worked example
Adding $200 monthly to principal is different from merely paying $200 early if the servicer applies it to a future scheduled payment. Confirm the application before relying on a payoff date.
Should every owner prepay?
No. Liquidity, rate, loan terms, and other uses of cash matter.
Questions landlords ask
Questions about this tool and its limits.
How does paying extra principal save interest?
Interest each month is charged on the remaining balance. Extra principal shrinks that balance faster, so less interest accrues every month after — and the loan finishes sooner. The earlier in the loan you add extra, the more it compounds in your favor.
Does the calculator include taxes and insurance?
No — it works with principal and interest only. Escrowed property taxes, homeowners insurance, HOA dues, and mortgage insurance aren’t part of the loan’s amortization, so they don’t change the payoff math shown here. Your actual monthly bill may include them.
Are there downsides to prepaying a mortgage?
Sometimes. A few loans carry prepayment penalties, and money put toward the mortgage isn’t available for other uses or investments. Confirm your loan allows extra principal without a penalty, and weigh the guaranteed interest saved against your other priorities.
Is this a guarantee of savings?
No. It’s an estimate built from the numbers you enter, assuming a fixed rate and that every extra payment is applied to principal. Real results depend on your loan’s terms, how the servicer applies payments, and whether you keep the extra payments up.
Keep exploring
More tools for buy & finance.
Mortgage calculator
Estimate monthly principal & interest, total interest, and total paid.
Open tool →
Loan-to-value (LTV) calculator
Estimate loan-to-value and the down payment behind it.
Open tool →
Amortization schedule calculator
Monthly P&I payment plus a year-by-year principal, interest, and balance table.
Open tool →
Editorial ownership
Written and maintained by the Aptoria editorial team
Editorial method reviewed July 28, 2026. Aptoria reviews scope, source fit, examples, limitations, links, and publication gates. This record does not claim attorney, CPA, lender, appraiser, or other independent professional sign-off.
Professional review is not claimed. Verify current law, tax treatment, loan terms, valuation inputs, and property-specific facts with the appropriate qualified professional before acting.
Built by a landlord who's done every one of these jobs by hand.
Aptoria was built by an owner-operator managing a Brooklyn portfolio — the 11pm calls, the awkward rent texts, the April receipt-pile — not by a software team guessing at the problem.
Stop sizing the problem. Let the agent run it.
Free for your first unit. The calculator gives you the number; Aptoria does the work — and you approve what matters.
Start free
Self-management software