---
title: "Extra Payment Calculator: Interest Saved | Yield Willow"
description: "See how extra monthly, yearly or one-off payments shorten a loan or mortgage: the new payoff date, months saved, interest saved and a yearly schedule."
url: https://yieldwillow.bond/extra-payment-calculator/
---

Loan calculator, 3 of 5

# Extra payment savings

A little extra toward principal shortens a loan more than you might guess. Try a monthly top-up, a once-a-year payment, a one-off lump sum, or all three.

**Educational use only — not financial advice.** Whether to prepay a loan depends on your whole situation; this only shows the arithmetic.

## Why extra payments go so far

Your regular payment stays the same. Any extra goes straight to principal, so every later month's interest is charged on a smaller balance, and more of each regular payment repays the loan. The effect compounds: the loan ends early and the months you skip at the end are the expensive part of the saving.

The calculator runs the schedule twice, once as agreed and once with your extras, and compares the payoff dates and total interest. Monthly extras start with the next payment, a yearly extra comes with every 12th payment, and a lump sum comes with the payment number you choose.

**Worked example:** $300,000 at 6.5% over 30 years has a payment of $1,896.20. Adding $100 a month pays it off in 26 years instead of 30 and saves $60,995.81 of interest.

Before paying extra, check that your lender applies it to principal and whether the loan has a prepayment penalty. The CFPB notes that such penalties usually apply to paying off the whole balance early, not to small extra payments.

## Sources

- Consumer Financial Protection Bureau, [What is a prepayment penalty?](https://www.consumerfinance.gov/ask-cfpb/what-is-a-prepayment-penalty-en-1957/)
- Consumer Financial Protection Bureau, Regulation Z, [Appendix J to Part 1026](https://www.consumerfinance.gov/rules-policy/regulations/1026/j/): the actuarial method, in which each payment first covers the interest earned on the unpaid balance and the rest reduces it.

## Questions

**Is one extra payment a year like biweekly payments?**

Close. Paying half the monthly amount every two weeks adds up to 26 half-payments, or 13 full payments a year. Entering one extra month's payment in "Once a year" approximates that, as long as your lender credits the money to principal.

**Does an extra payment lower my monthly payment?**

Not on a standard fixed-rate loan: the payment stays the same and the loan ends sooner. Some lenders will recalculate (recast) the payment after a large lump sum, usually for a fee; ask yours.

**Can I use a balance part-way through a loan?**

Yes. Enter today's balance from your statement, the rate and the years left. The regular payment is worked out from those figures, so it may differ by a few cents from what you pay now.