Mortgage Payoff Calculator
Estimate how fixed extra monthly principal changes a mortgage payoff date and remaining interest.
Content updated August 2, 2026
This is a monthly fixed-rate estimate, not a lender payoff statement. It excludes daily interest, escrow, fees, and possible prepayment penalties. Confirm that extra funds will be applied to principal.
Extra principal reduces the balance used to calculate later interest. This calculator compares the remaining fixed-rate schedule with a second schedule that adds the same extra-principal amount every month.
Enter the current principal balance, nominal annual interest rate, remaining term, and planned extra amount. The result estimates the accelerated payoff time, months saved, remaining interest, interest saved, and smaller final payment.
The Mortgage Payoff formula
M = P[r(1+r)^n]/[(1+r)^n−1]; each month: B₁ = B₀ + B₀r − min(B₀+B₀r, M+E)P = current balance · r = nominal annual rate ÷ 12 · n = remaining months · M = scheduled principal-and-interest payment · E = fixed extra monthly principal · B = balance. At r = 0, M = P ÷ n.
Worked example
For a $200,000 balance at 6% with 30 years remaining, the scheduled payment is about $1,199.10. Adding $200 each month produces an estimated payoff in 252 months instead of 360, about 108 months sooner, with roughly $79,800.51 less interest in this monthly model.
Assumptions, rounding, and limitations
Assumptions
- The mortgage has a fixed nominal annual rate and interest accrues monthly at that rate divided by 12.
- The scheduled payment is recalculated from the current balance and remaining whole-month term.
- The same non-negative extra amount is paid every month and is applied immediately to principal.
- All money inputs and outputs use the selected currency unit.
Rounding: The payoff simulation retains full floating-point precision. Currency displays use up to two decimal places, while payoff time is a whole count of monthly payments.
Limitations
- Supports balances and extra payments up to 1 trillion, annual rates from 0% to 100%, and remaining terms from 1 month to 100 years.
- Excludes daily-interest conventions, changing rates or payments, skipped payments, escrow, fees, mortgage insurance, prepayment penalties, and lender-specific allocation or rounding.
- The result is not a lender payoff statement and does not establish whether a contract permits penalty-free prepayment.
Sources
- What is a payoff amount, and is it the same as my current balance? — Consumer Financial Protection Bureau
- What is a prepayment penalty? — Consumer Financial Protection Bureau
- Your mortgage servicer must comply with federal rules — Consumer Financial Protection Bureau
How monthly extra principal changes the schedule
The calculator first finds the scheduled principal-and-interest payment that would amortize the current balance over the entered remaining term. Each simulated month then adds interest at the nominal annual rate divided by 12 and applies the scheduled payment plus the extra amount.
When the remaining balance plus that month's interest is smaller than the planned payment, the final payment is reduced to exactly that amount. The model therefore does not subtract a full payment after the loan has already reached zero.
Why a lender payoff quote can differ
A current statement balance is not necessarily the amount required to close the loan on a particular day. The CFPB explains that a payoff amount can include interest through the payoff date, unpaid fees, and a prepayment penalty when the contract permits one.
Servicers may also use daily interest and contractual rounding rather than this monthly model. Treat this result as scenario planning, then request a dated payoff statement and confirm how the servicer applies additional funds.
Frequently asked questions
▶Does an extra mortgage payment go entirely to principal?
Only if the servicer applies it that way. Confirm the lender's instructions and check the statement after payment rather than assuming every amount above the bill automatically reduces principal.
▶Can this estimate my exact mortgage payoff quote?
No. A lender quote may include daily interest, fees, escrow adjustments, or a permitted prepayment penalty that this monthly estimate excludes.
▶What happens if I enter zero extra principal?
The accelerated and baseline schedules are the same, so months saved and estimated interest saved are zero.
▶Why can an early extra payment save more interest?
Reducing principal earlier lowers the balance on which later interest is calculated, so the benefit continues through every remaining month.
▶Does the calculator include taxes and insurance?
No. It models principal and interest only. Escrowed property taxes, insurance, mortgage insurance, and other housing costs do not reduce the loan balance.
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Open calculator →Disclaimer: Mortgage Payoff Calculator results are estimates for general information and education only, and are not financial, tax, legal or medical advice. Verify important decisions with a qualified professional.