OraMake the comparison consistent
The baseline uses the fixed-rate monthly payment formula. In the extra-payment scenario, the chosen extra amount is added to each scheduled payment and applied after that month's interest. The loan ends when the outstanding balance and final interest are cleared.
The estimate assumes no prepayment fee, no missed payment, a constant rate and immediate principal reduction. It keeps the regular payment unchanged, shortening the term. A lender that recalculates the payment instead can produce a different outcome.
An extra 50.00 each month
For 10,000.00 at 6% over 36 months, the regular rounded payment is 304.22. The baseline cent-rounded schedule has 951.88 of interest. Paying 354.22 each month clears the balance in 31 months, with a final payment of 180.69.
Interest in the extra-payment schedule is 807.29: a reduction of 144.59 and five payment months compared with the baseline. These are model results before any extra-payment charge.
Verify how the lender treats an extra payment
Ask whether extra money reduces principal, advances a future due date or is handled another way. Check annual overpayment allowances, penalties and whether an instruction is needed. CFPB: mortgage prepayment penalties explains that some mortgage agreements can charge for early repayment.
A modeled interest reduction is not a recommendation to use every spare amount for debt. Keep required payments, liquidity needs and other commitments in the comparison.
The overpayment-interest guide follows how an earlier principal reduction affects later interest and why lender treatment matters. For the underlying monthly balance mechanics, read the amortization walkthrough.
Read savings as a schedule difference
Interest saved is baseline interest minus extra-payment interest. It is not the sum of the extra deposits: those payments repay principal you already owed. Monthly interest is rounded to minor units, so a hand calculation using an unrounded formula can differ by a few cents.
Common questions
Does an overpayment always shorten the loan?
Only under the modeled convention that the lender applies extra money to principal and keeps the regular payment unchanged. Check your agreement.
Are early-repayment penalties included?
No. Add verified charges separately before comparing total cost.
Is the extra money counted as a saving?
No. It is additional principal repayment. The reported saving is the reduction in modeled interest, before fees.
Educational estimate using the stated assumptions. Fees, taxes, changing rates and individual circumstances can change an outcome. This is not personalized financial advice. Read the estimates disclaimer.