Calculyn

Mortgage Extra Payment Calculator

Find out how much extra principal each month shortens your mortgage and saves in interest.

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Results are estimates for planning and are not financial advice.

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Quick answer

Adding $200 a month to a $300,000, 6.5%, 30-year mortgage pays it off nearly 7 years early and saves roughly $100,000 in interest.

How it works

Every extra dollar goes straight to principal, so you pay interest on a shrinking balance. Even a modest extra payment can cut years off a 30-year mortgage.

Formula

Each month: Balance = Balance + Interest − (Payment + Extra)

Assumptions & limitations

  • Extra payment starts immediately and stays constant
  • No prepayment penalty
  • Fixed interest rate

Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators

Frequently asked questions

Should I pay extra or invest the money?

Paying extra guarantees a return equal to your mortgage rate; investing may earn more but with risk.

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

Usually yes — mark extra payments as 'principal only' so they aren't treated as early regular payments.