PayoffTable

Early Mortgage Payoff Calculator

Every other calculator asks "what happens if I pay $X extra?" This one reverses it: you pick the year you want the mortgage gone — say, the year your kid graduates — and it solves for the monthly extra that gets you there.

Reviewed by the PayoffTable editorial team · Updated 2026-10-24

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Goal-first thinking changes the conversation. "Should I pay extra?" has no answer; "what would it take to be done by 2040?" does. The required number is often smaller than people fear — on a $280,000 balance at 6.5% with 26 years left, being mortgage-free in 15 years takes about $492 a month in extra principal, and saves over $167,000 in interest.

There is a hard floor worth knowing: no monthly extra can beat the math of a lump sum you do not have. If your goal is geometrically impossible at your balance and rate, the calculator says so instead of returning a fantasy number. When that happens, the honest paths are a longer goal, a recast-plus-extra hybrid, or refinancing to a shorter term.

Treat the result as a ceiling, not a commitment. Any month you hit the target extra, you are on pace; any month you fall short, the schedule simply stretches — extra payments have no penalty and no minimum.

How the goal-reverse calculation works

There is no closed-form formula for "required extra to hit a target month with a fixed base payment," so this calculator solves it numerically: it repeatedly simulates the month-by-month schedule with different extra amounts until the payoff month matches your goal to within one month. Sixty bisection iterations is enough for sub-penny precision.

The base payment itself comes from your current balance, rate, and remaining term — the loan you actually have, not the original loan you signed years ago. That matters: if you have already been prepaying, your remaining term is shorter than the original, and the required extra to finish by a given date is correspondingly smaller.

find x : months(balance, rate, remaining, extra = x) = goal (solved by bisection, ±1 month)

Impossibility check: if even paying the entire balance amortized over your goal term (base payment + maximal extra) lands past the goal, the goal is unreachable with monthly extras alone, and the calculator tells you so. That maximal-payment bound is PMT(balance, rate, goalMonths).

Worked example. Balance $280,000 at 6.5%, 26 years remaining, goal: paid off in 15 years. Required extra: $577.33/month (base payment $1,861.77). New payoff: Nov 2041. Interest saved vs. the original schedule: $141,833.99. Miss by a bit — an 18-year goal needs only $340.60/month.

Terms & definitions

Amortization
The process of paying off a loan with scheduled payments that cover both interest and principal. Early payments are mostly interest; later payments are mostly principal.
Principal
The amount you borrowed and still owe. Extra payments reduce principal directly, which shrinks every future interest charge.
APR
Annual Percentage Rate — the yearly cost of the loan including fees. Your monthly interest charge uses the note rate, which is usually a touch lower.
Term
The number of years the loan is scheduled to last. A 30-year term has lower payments but roughly double the total interest of a 15-year term at the same rate.

Frequently asked questions

What if my goal is impossible?
The calculator says so explicitly. The geometric limit is paying your full balance amortized across the goal period — if that payment is not affordable, no monthly extra alone can hit the goal. Options: extend the goal by a year or two, combine a lump sum (recast or curtailment) with monthly extras, or refinance to a shorter term.
Should I round the required extra up?
Rounding up to a clean number ($500 instead of $491.93) is free acceleration — every dollar still goes to principal. Rounding down quietly moves your payoff date later, usually by weeks per dollar of rounding.
Does this account for extra payments I already made?
Yes, indirectly: enter your current balance and remaining term from a recent statement, not the original loan. Those numbers already reflect everything you have prepaid, so the solved extra is what you need from today forward.
Is an early payoff goal better than refinancing to 15 years?
They are the same math wearing different paperwork. The 15-year refinance locks the discipline in at a possibly-lower rate but costs $2,000–$6,000 in closing costs and a credit check; the DIY extra-payment version keeps your current loan, costs nothing, and flexes when life happens. Our 15 vs 30 year guide covers the tradeoff in full.

References

  1. Consumer Financial Protection Bureau — Loan Estimate explainer (how principal, interest, and amortization appear on your closing documents)
  2. CFPB — What is an amortization schedule?
  3. Federal Reserve — Mortgage origination resources (APR vs note rate)
Educational content only — not financial, tax, or legal advice. Your loan terms govern; confirm details with your servicer.

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