Amortization & Mortgage Payoff Forecast
Mortgage amortization calculator: a yearly table with monthly extra principal or a 13-payment budget, showing payoff, interest and the real last payment.
What This Calculator Does
Type in a fixed-rate loan and you get a full money summary plus a yearly table, all the way to payoff. The run begins at your opening principal and lasts the whole term you choose. Think of each month as a cycle: interest accrues, then the scheduled P&I and any extra principal post at its end. The 13-payment option is a monthly-equivalent stand-in for a yearly budget. It does not mirror how a real biweekly plan posts.
Who Is This For
Want to see what extra principal does to a hypothetical loan? This page runs that comparison in U.S. dollars, on a monthly P&I basis. If you're checking a loan you already hold, bring a matching balance and remaining term. Payments you made in the past are not rebuilt.
How It Works
Begin with your principal and a fixed nominal yearly rate. Next come the full term and the payment method, and the monthly convention needs a check against your loan. Extra-monthly mode wants an explicit extra typed in, even 0. Blanks and sample values are not confirmed loan terms. Before you rely on the output, scan the planned and actual last payment, the savings versus no extra, and every yearly row. Verify posting and payoff instructions separately.
Frequently Asked Questions
What does this forecast compute?
Expect the scheduled monthly P&I, the extra budget you picked and the planned monthly cash. Then come the payoff month, the real last payment, total interest and total payments. You also see the savings versus a no-extra run, the extra principal truly used, and each yearly row until payoff. The math begins with the debt you entered and runs the full term you chose. What it will not do: guess at payments already made, current statement balances, fees or loan approval.
Does paying with the 13-payment option mimic a true biweekly plan?
No. The 13-payment option only matches a biweekly plan's yearly total. Each month it adds the scheduled P&I divided by 12 to principal, so a year's budget works out to 13 monthly scheduled payments. Work it from 26 half-payments and the answer is 13 again. A matching total says nothing about whether real payments fall on 14-day dates, how a servicer credits part of a payment, or whether interest is charged daily. Putting the same yearly extra in at year-end could shift payoff and interest.
Is my extra principal already inside the scheduled payment?
No. The scheduled payment is P&I and nothing more. On top of it sits the extra budget, which you either typed or the tool derived. Planned monthly cash is scheduled P&I plus that extra, and both are applied at the same moment, the end of the month. In the final month the payment can come in smaller than planned. Because interim values aren't rounded, a monthly-equivalent extra may hold fractions of a cent.
Can my final payment end up larger than the balance?
No. In the final month, actual cash stops at the principal still owed plus that month's interest, and the model ends there. Whatever budget is left isn't counted as paid. That makes total extra applied equal to the cash used beyond the scheduled P&I, which will not match the requested extra times the number of payments. The yearly principal figure has the used extra built in, so adding it separately would double-count.
What explains the gap between my bank statement and this projection?
Mostly rounding and bank rules. Here, payments, balances and interest stay exact month to month, and only the displayed values get rounded. Your bank may round charges to the cent, count dates differently, or apply partial-payment rules of its own. A leftover balance under half a cent is not forgiven in this model. Treat the cents you see as a projection, not a promise about real billing. Closing out the loan means requesting a payoff quote from your servicer.
Will the tool accept a zero rate, or zero in the extra field?
Yes to both. A 0% rate is a valid what-if, but it doesn't mean a loan like that exists for you to take. Type $0 in extra-monthly mode and you get a schedule identical to having no extra at all. Leave the field blank and the tool reads it as unknown, never as 0. Standard and monthly-equivalent modes slip in no hidden extra. Pick from 10, 15, 20, 25 and 30 years; that menu says nothing about what a lender will approve.
What goes into the interest-saved figure and the year-by-year rows?
Think of savings as the gap between your plan and a run with no extra, using the identical opening principal, rate and term. That gap is counted in nominal modeled interest and months. It is not an investment return, and it doesn't point to the lowest-total-cost choice. In the table, yearly principal already holds the extra, interest is listed apart, and a final partial year stays. The full table shows in the result and the PDF. The AI briefing draws on the full 11-metric money summary and on every yearly row.
Which items belong on my list for the loan servicer?
Your servicer holds the answers, so ask. Is the note rate what you modeled? Do the opening debt and term match? How will extra principal be allocated, on which posting dates, and is there a prepayment penalty? As of September 30, 2026, CFPB servicing guidance says partial payments may wait until a full sum arrives. That guidance does not check your rate and does not predict any specific biweekly plan. This math leaves out escrow, taxes, insurance, HOA and fees. Closing the loan takes a real payoff quote.