See how much interest and time you save by adding extra principal to your monthly mortgage payment.
Calculations follow the month-by-month amortization your lender uses.
A small extra payment toward principal every month can shave years off a 30-year mortgage. This tool runs the amortization both ways — baseline versus accelerated — so you can see exactly how many months and dollars of interest you avoid.
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.
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