What can extra principal payments save?
An extra payment toward principal reduces the balance used to calculate future interest. In this calculator, you keep making the original scheduled payment plus a recurring extra amount until the balance reaches zero.
The example below compares four schedules for the same loan. It is a calculation example, not a forecast of what every borrower will save. Updated October 3, 2026.
Compare $50, $100 and $200 extra per month
Assumptions: $300,000 borrowed, 6.5% fixed annual interest, a 30-year term, and monthly payments. Extra principal begins with the first payment and continues every month. No taxes, insurance, fees or prepayment charges are included.
| Extra / month | Payment* | Payments | Total interest | Interest saved |
|---|---|---|---|---|
| $0 | $1,896.20 | 360 | $382,633.47 | $0.00 |
| $50 | $1,946.20 | 334 | $349,051.74 | $33,581.73 |
| $100 | $1,996.20 | 312 | $321,638.68 | $60,994.79 |
| $200 | $2,096.20 | 277 | $279,184.67 | $103,448.79 |
*Regular principal and interest plus the extra amount; the final payment is smaller. Calculations use full precision internally. With $100 extra in this example, the loan takes 48 fewer monthly payments and incurs about $60,995 less interest.
Why the first extra $100 matters
Without extra principal, the first payment reduces this loan’s balance by about $271.20. Adding $100 raises that principal reduction to about $371.20. The following month’s interest is calculated on the smaller remaining balance. Repeating this process changes both total interest and the number of payments.
Try your own loan numbers
- Open the amortization calculator with extra payments and enter the loan amount, stated interest rate and term.
- Calculate once with zero extra principal to see the baseline.
- Enter a recurring extra amount and calculate again. Compare total interest, payments saved and the final table row.
- Download or print the schedule you want to keep.
This input models the same extra amount each month. It does not model a single lump sum, occasional payments, a later starting month, or biweekly payments.
Check how your servicer applies the money
Ask your servicer how to designate additional money for principal and check the payment history afterward. The CFPB’s mortgage servicing guidance explains why correct payment application matters.
Some loans have prepayment penalties. Check your own loan terms before relying on a savings estimate; the calculator does not subtract these charges. Read the CFPB’s explanation of prepayment penalties.
Does an extra payment lower the monthly bill?
This model leaves the original scheduled payment unchanged and estimates an earlier payoff. It does not model a recast or refinance. If your goal is a lower required monthly payment, ask your lender what options your loan allows.
For help interpreting individual rows, see how to read an amortization table. Estimates support planning; your lender’s schedule and payoff quote govern your actual loan.
Calculate your extra-payment savings →