mCalculator logo
Mortgage Calculators

Extra Mortgage Payment Calculator

Mortgage calculator with extra payments to principal — see how much interest and time you save by adding an extra monthly principal payment.

Calculations follow the month-by-month amortization your lender uses.

$
%
yr
$
Interest saved
$108,097
And 6 yr 2 mo off your mortgage.
Baseline payoff
30 yr
Accelerated payoff
23 yr 10 mo
Baseline total interest
$446,406
New total interest
$338,309
Explain this result

Turn the numbers above into plain-language takeaways. Educational only — not financial advice.

Save & Compare Scenarios

Save the current inputs under a name, then reload or compare them side by side. Scenarios stay on this device only.

Overview

How the Extra Mortgage Payment Calculator Works

A small extra principal payment every month can shave years off a 30-year mortgage. This is a mortgage calculator with extra principal payments built in — it runs the amortization both ways, baseline versus an extra monthly mortgage payment applied straight to principal, so you can see exactly how many months and dollars of interest you avoid when you make extra payments to principal.

Formula

The Math Behind the Calculator

Each month: interest = balance × monthly rate. The scheduled payment minus interest goes to principal; any extra you add comes off principal too. Repeat until the balance reaches zero, then compare against the baseline schedule.

Example

A Worked Example

On a $350,000, 30-year loan at 6.5%, an extra $200 per month pays the loan off about 5 years and 8 months early and saves roughly $90,000 in interest. An extra $400 per month saves around 9 years and $147,000.

How to use

How to Use the Extra Mortgage Payment Calculator

  1. 1Enter your loan amount, rate, and original term.
  2. 2Add the extra monthly amount you want to put toward principal — even $50 helps.
  3. 3Compare baseline payoff to accelerated payoff and decide if the savings justify the lifestyle trade-off.
Interpretation

What the Results Mean

  • Months saved is how much sooner you're mortgage-free.
  • Interest saved is real money — it never leaves your bank account in the first place.
  • If interest saved is dramatically large, your loan is heavily front-loaded with interest, which is typical for early years of a long mortgage.
Keep exploring

Smart Next Steps

What to explore next
Avoid

Common Mistakes to Avoid

  • Sending extra money without marking it 'principal only' — some servicers apply it to the next scheduled payment instead.
  • Paying extra on a 3% mortgage when the same money would earn more in a high-yield savings account or index fund.
  • Skipping the emergency fund to make extra payments — your home doesn't pay you back when you lose your job.
Keep going

Related Calculators

Mortgage Payment Calculator

Estimate your monthly mortgage payment including principal, interest, property taxes, insurance, HOA, and PMI.

Mortgage Refinance Calculator

Calculate monthly savings, break-even point, and lifetime interest if you refinance your mortgage.

15 vs 30 Year Mortgage Calculator

Compare monthly payments and lifetime interest between a 15 year and 30 year mortgage at real rates.

Mortgage Amortization Calculator

Generate a full month-by-month amortization schedule for any mortgage, with the principal/interest split and running balance for every payment.

Learn

Related Guides

9 min read

Mortgage Calculator With Extra Payments to Principal: How It Works

What actually happens when you add extra money to principal, how a mortgage calculator with extra payments models it, and how many years each amount can cut.

Read guide
6 min read

Extra Mortgage Payments: 3 Strategies That Actually Work

Compare biweekly, monthly extra principal, and lump-sum strategies. See how much each shaves off a real $400K, 30-year mortgage.

Read guide
FAQ

Frequently Asked Questions

How do extra principal payments affect a mortgage?+

Every extra dollar applied to principal reduces the balance interest is charged on for every remaining month. That compounds — even a modest extra monthly payment can cut years off a 30-year loan and save tens of thousands in interest.

Is it better to make one extra mortgage payment a year or add extra monthly?+

Adding a smaller amount each month saves slightly more interest than a single lump sum at year end, because principal comes down sooner. Both beat the baseline; pick whichever you'll actually stick with.

Should I pay extra monthly or one big lump?+

Mathematically very similar. Monthly is easier to budget; lump sums (such as a bonus) work well if you have variable income.

Do I need to tell my lender it's principal?+

Usually yes. Check the servicer's instructions — most have a 'principal-only payment' option in their online portal.

What about prepayment penalties?+

Rare on residential mortgages today, but check your loan documents to be sure.

Financial Disclaimer

This calculator is for educational and estimation purposes only. It does not provide financial, mortgage, tax, investment, or legal advice. Actual rates, payments, taxes, fees, insurance costs, eligibility, and loan terms vary by lender, location, credit profile, and market conditions. Always compare official offers and consult a qualified professional before making financial decisions.

Last updated June 2026 · Prepared by the mCalculator Editorial Team