Extra Mortgage Payment Calculator

Q: Does an extra payment automatically go to principal?

Follow the mortgage servicer’s instructions, identify the amount as additional principal, and verify the posting.

Q: Will an extra mortgage payment lower my required monthly payment?

Usually not. Extra principal may shorten the payoff period while the contractual payment remains unchanged; a recast is a separate process.

Q: Could there be a prepayment penalty?

Some loans have one. Review the note and confirm the terms with the mortgage servicer before a large payment or early payoff.

Let’s rebuild the mortgage from your most recent statement.

Step 1 · Your current loan

What do you still owe?

Use the unpaid principal balance, note rate, and remaining term. Do not use the original home price or a payoff quote that includes daily interest and fees.

If you do not know the payment: I’ll estimate principal and interest from the other three answers. Your statement is the better source when the loan has been modified or recast.

Current principal balance

Current note rate

Use the note rate, not APR.

Years remaining

years

You may enter a half year, such as 26.5.

Scheduled monthly principal and interest

Leave blank to use the calculated amount. Exclude escrow and HOA dues.

Your estimated scheduled principal-and-interest payment is being calculated.

Now tell me what you could add without making the rest of your budget fragile.

Step 2 · Monthly extra principal

What could you add each month?

This amount is modeled as extra principal after the scheduled payment. The tool does not assume that “paying ahead” automatically reduces principal.

Recurring monthly extra

Enter the exact amount you want modeled as extra principal each month.

Your monthly plan is being calculated.

How should I send an extra payment?

Follow your servicer’s instructions and identify the amount as additional principal. A servicer may otherwise treat money as a future installment or hold a partial payment. Confirm the posting on the next statement.

Monthly payments are not the only way people accelerate a loan.

Step 3 · Annual and one-time payments

Do you expect any larger principal payments?

Use the annual field for a recurring bonus or the “one extra payment a year” approach. Use the lump-sum field for one known payment. Both remain optional.

Extra principal once each year

Modeled after every twelve scheduled payments.

One-time lump sum

When would the lump sum be paid?

months from now

The payment has no modeled effect until this month.

No annual or lump-sum principal is currently included.

Could a large payment lower my required monthly payment?

Not by itself. Extra principal usually shortens the payoff path while the contractual payment stays the same. Some servicers may offer a recast after a substantial principal payment. That is a separate request with its own eligibility, timing, and possible fee.

If you have a date in mind, let’s work backward from it.

Step 4 · Payoff target

When would you like the balance to reach zero?

This helper estimates the recurring monthly extra needed to reach your target using the current balance and note rate. It does not include the annual or lump-sum entries above.

Desired payoff period

years

Your target amount is being calculated.

Here is what your extra-principal plan changes—and what it does not.

Your answer

PLANNING ESTIMATE · NOT A PAYOFF QUOTE

Your payoff plan is being calculated.

Time saved—

Interest avoided—

Accelerated payoff—

Balance timeline

How quickly do the two payoff paths separate?

Lower means less principal remains. Choose a year to see the exact balances rather than estimating from the lines.

Compare year 5

After 5 years

Scheduled balance—

Accelerated balance—

Additional equity—

Extra principal contributed—

Scheduled payoff—

Accelerated payoff—

Difference—

Change one answer without starting over

Edit the current loan Edit the monthly extra Edit annual or lump-sum payments Edit the target date

Want me to quality-check and email this plan?

You can use the calculator freely. To retain the personalized result, send your email and I will review the entries before sending it. No cost. No obligation.

What I would want you to understand before paying extra

Does an extra payment automatically go to principal?

Do not assume it does. Follow the servicer’s instructions, identify the amount as additional principal, and confirm the posting on the next statement. Partial or early payments may be handled differently from an identified principal curtailment.

Will my required monthly payment go down?

Usually not. Extra principal can shorten the payoff period while the contractual payment remains unchanged. A loan recast is a separate process that may reduce the required payment after a substantial principal reduction.

Is one extra payment a year the same as biweekly payments?

Paying half the monthly amount every two weeks produces 26 half-payments, or 13 full-payment equivalents, in a year. Whether and when the servicer applies those partial payments matters. This calculator’s annual-extra field gives you the same planning concept without assuming a servicer’s biweekly program.

Could there be a prepayment penalty?

Some mortgages have one. CFPB says penalties do not normally apply to small extra-principal payments, but you should check the note and ask the servicer before a large lump sum or early payoff.

Does paying extra remove mortgage insurance?

It may help the balance reach an eligibility threshold sooner, but cancellation rules depend on the loan program, payment history, property value, and servicer. This calculator does not model a mortgage-insurance cancellation date.

Should I pay the mortgage or keep the cash?

The calculator does not make that recommendation. Emergency reserves, repairs, other debt, retirement contributions, taxes, investment risk, and how long you expect to own the home can matter. The result only shows the mortgage arithmetic.

Why does the lump-sum timing matter?

An earlier principal reduction generally avoids more future interest because more later monthly interest calculations use the lower balance. The model applies the lump sum in the month you select.

Is this the amount needed for an official payoff?

No. A payoff statement can include daily interest and other amounts through a specific date. Request the current written payoff figure from the servicer when a sale, refinance, or full payoff is actually planned.

Use this as a planning conversation, not a lender instruction.

Educational estimate. This tool provides a planning estimate based on the information you enter and the assumptions shown. It is not financial, lending, legal, tax, insurance, appraisal, or settlement advice; a payoff statement; a servicing instruction; a credit decision; or a guarantee of savings or future results. Verify the balance, payment, posting rules, prepayment terms, and figures that matter with your mortgage servicer and appropriate advisers.

No brokerage relationship is created. Using this tool, requesting results, submitting a form, or contacting Ask A Walker does not by itself create a client, agency, brokerage, fiduciary, or other professional relationship. In Virginia, representation is governed by a separate written brokerage agreement signed by the applicable parties.

How the estimate is built

The engine models monthly interest on the opening principal balance, applies the scheduled principal-and-interest payment, and then applies the extra principal entered for that month. It excludes escrow, taxes, insurance, HOA dues, mortgage-insurance cancellation, daily interest, fees, and investment returns.

Research last reviewed: August 21, 2026. Next scheduled review: November 2026.

How much sooner could you pay off your mortgage?

Your normal payment and your extra principal do different jobs.