Extra Mortgage Payment Savings Calculator

How Extra Mortgage Payments Work Every dollar you pay above your required monthly payment goes directly to reducing your principal balance. A lower principal means less interest accrues each month, which creates a compounding snowball effect. Even a modest extra $100–$200/month can cut years off your mortgage and save tens of thousands in interest.

Standard Monthly Payment Formula P = L × [r(1+r)^n] / [(1+r)^n − 1]

Where:

• P = monthly payment
• L = loan balance
• r = monthly interest rate (annual rate ÷ 12)
• n = total number of payments (years × 12)

Amortization With Extra Payments Each month, interest accrued = remaining balance × monthly rate. The regular payment covers that interest plus a small slice of principal. Your extra payment eliminates additional principal directly, compressing future interest.

Worked Example Loan: $300,000 | Rate: 6.5% | Term: 30 years | Extra payment: $200/month

Normal monthly payment: $1,896 Total interest with no extra: $382,633 Total interest with the extra: $279,185 Interest saved: $103,449 Time saved: 6 years 11 months

Run those numbers through the calculator above and it returns exactly these figures.

Why This Matters So Much In the early years of a mortgage, most of your payment is interest, not principal. On a $300k loan at 6.5%, the first payment is roughly $1,625 interest and only $271 principal. Extra payments attack principal when it matters most, cutting the most expensive early interest.

Refinancing vs Extra Payments Refinancing to a lower rate can save more, but it has closing costs. Extra payments are free, flexible, and reversible (you can stop anytime). Both strategies can be combined for maximum effect.

This page does one strategy on purpose It takes the loan from its start and answers a single question: what does a fixed extra amount every month buy?
If you are partway through the mortgage and want the balance and remaining term instead, or you want to see extra-monthly weighed against an annual lump sum, rounding the payment up, or one windfall paid today, that is the mortgage payoff strategy comparison.
Both pages simulate the loan month by month and agree to the dollar on the shared case above.