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.
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.
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.
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.
Estimate your monthly mortgage payment including principal, interest, property taxes, insurance, HOA, and PMI.
Calculate monthly savings, break-even point, and lifetime interest if you refinance your mortgage.
Compare monthly payments and lifetime interest between a 15 year and 30 year mortgage at real rates.
Generate a full month-by-month amortization schedule for any mortgage, with the principal/interest split and running balance for every payment.
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.
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.
Mathematically very similar. Monthly is easier to budget; lump sums (such as a bonus) work well if you have variable income.
Usually yes. Check the servicer's instructions — most have a 'principal-only payment' option in their online portal.
Rare on residential mortgages today, but check your loan documents to be sure.
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