What an Extra $200 a Month Does to a 30-Year Mortgage

On an amortising loan, an extra payment does something structurally different from a normal one. Understanding why explains the size of the effect.

Where the money goes

A scheduled payment is split. Part covers the interest accrued since the last payment; the rest reduces principal. Early in the loan, most of it is interest, which is the mechanism covered in how loan amortisation works.

An extra payment is different. The interest for the period has already been covered by the scheduled payment, so an additional amount applied to principal reduces the balance directly. And because all future interest is calculated on the balance, that reduction eliminates every interest charge that principal would have generated for the remaining life of the loan.

That is the whole effect. You are not buying a discount; you are deleting future interest.

The numbers on a 30-year mortgage

Take $250,000 at 6.5% over 30 years. Principal and interest come to about $1,580 a month.

Paying as scheduled: 360 payments, and total interest of about $318,861. You pay more in interest than you borrowed.

Adding $200 a month: the loan clears in 265 months, a little over 22 years, with total interest of about $221,243.

The extra $200 a month:

• Saves roughly $97,600 in interest
• Ends the loan 95 months early, just under eight years

Total extra paid in is about $53,000. It removes $97,600 of interest. That ratio is the compounding effect running in your favour, and it is why extra payments early in a loan are so much more powerful than the same payments late.

Run your own balance and rate through our loan calculator and compare total interest across different terms to see the same effect on your numbers.

You have to tell the servicer where to put it

This is the practical trap. Send extra money without instruction and a servicer may:

• Hold it and apply it to next month's scheduled payment, which achieves almost nothing
• Park it in suspense until it adds up to a full payment
• Apply it to escrow rather than principal

Any of these can mean your extra payment does not reduce principal at all. You generally need to state explicitly that the additional amount is to be applied to principal, and then confirm on the next statement that the balance moved by the amount you expected. The CFPB advises checking that extra payments are credited as you intended rather than assuming.

Check for a prepayment penalty first

Some loans charge for paying ahead or paying off early. Prepayment penalties are restricted on many mortgages and are more common on other loan types. Read the note, or ask the servicer directly what happens if you overpay. A penalty does not always make prepaying wrong, but it changes the arithmetic.

When not to do this

Prepaying a loan is a guaranteed return equal to the loan's interest rate. That is genuinely good, and there are still several things that beat it:

• Higher-rate debt. Paying down a 24.99% card before a 6.5% mortgage is not close
• An unclaimed employer retirement match. An immediate 50% or 100% on the matched portion is a better return than any mortgage rate
• No emergency fund. Money paid into a mortgage is not accessible when the car fails. Home equity is not liquid, and needing to borrow it back later is expensive. See building an emergency fund
• A low fixed rate. If your rate is well below what a savings account pays, the arithmetic can favour saving instead

The ordering matters more than the enthusiasm. Prepaying a cheap mortgage while carrying an expensive card balance is a common and costly mistake.

Sources

• CFPB: What is amortization?
• CFPB: Loan options
• CFPB: What is a personal loan?

Current as of August 2026. The loan amount and 6.5% rate are illustrative; figures cover principal and interest only, excluding taxes, insurance and escrow. Totals computed with monthly compounding.