Extra Principal for Payoff Date Calculator
Find the extra monthly principal you must add to pay off your loan by a target date, and the interest that acceleration saves.
How it works
Required payment = balance × r ÷ (1 − (1+r)^−n), where n = target months · Extra = required payment − current payment
To hit a specific payoff date you solve the amortization formula for the payment that clears the balance in the number of months you have left. The difference between that payment and your current one is the extra principal to add each month. Because you cut the balance faster, less interest accrues — the shorter the target, the larger both the payment and the savings.
Worked example
On a $240,000 balance at 6.25% currently paying $1,750/mo, paying it off in 15 years needs about $2,058/mo — roughly $308 extra. That acceleration saves tens of thousands in interest compared with the original, longer payoff schedule.
Frequently asked questions
Does extra principal really save that much interest?
Yes. Every extra dollar goes straight to principal, so it stops accruing interest for the entire remaining life of the loan — the effect compounds over the years you cut off the schedule.
Should I tell my lender the payment is extra principal?
Yes — mark additional amounts as "apply to principal," or some servicers treat them as prepaying the next scheduled payment instead of reducing the balance.
Is there a penalty for paying early?
Most modern mortgages have no prepayment penalty, but some loans do, especially in the first few years. Check your note before making large extra payments.
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Educational estimate, not financial advice. Confirm figures with your lender or a licensed professional.