# Extra payment and amortization calculator

> See how extra principal payments cut your mortgage interest and payoff date, with a full amortization schedule and a balance chart that updates live.

URL: https://mortgage-math-us.com/tools/extra-payment-calculator/  
Last reviewed: 2026-10-28 · By the MortgageMath US Editorial team

## Quick answer

Extra principal lowers the balance immediately, so less interest accrues every month after. On a $325,000 30-year loan at 7.24%, paying $200 extra each month saves about **$126,421 in interest** and pays the loan off **6 yr 10 mo early**. Tell your servicer to apply the extra to principal.

## Key facts

| Fact | Value | Source | As of |
|---|---|---|---|
| 30-year fixed average (default rate) | 7.24% | [Freddie Mac Primary Mortgage Market Survey](https://www.freddiemac.com/pmms) | Week of Oct 29, 2026 |
| 15-year fixed average | 6.6% | [Freddie Mac Primary Mortgage Market Survey](https://www.freddiemac.com/pmms) | Week of Oct 29, 2026 |
| PMI ends automatically at | 78% | [CFPB](https://www.consumerfinance.gov/ask-cfpb/when-can-i-remove-private-mortgage-insurance-pmi-from-my-loan-en-202/) | Oct 28, 2026 |
| You can ask to cancel PMI at | 80% | [CFPB](https://www.consumerfinance.gov/ask-cfpb/when-can-i-remove-private-mortgage-insurance-pmi-from-my-loan-en-202/) | Oct 28, 2026 |
| Longest Qualified Mortgage term | 30 years | [CFPB](https://www.consumerfinance.gov/ask-cfpb/what-is-a-qualified-mortgage-en-1789/) | Jan 7, 2025 |

## How amortization works

Each monthly payment on a fixed-rate loan is the same, but its make-up changes. Interest is charged on the balance still owed, so early payments are mostly interest and later ones mostly principal. In the first year of a $325,000 loan at 7.24%, $23,427 of the $26,578 you pay goes to interest and only $3,152 to principal.

An extra payment skips the interest entirely: it lowers the balance the next month’s interest is calculated on. That is why a modest amount early in the loan saves far more than the same amount near the end.

## What different extra payments save

*$325,000 loan, 30-year fixed at the 7.24% average — interest saved and time cut versus the regular schedule*

| Extra principal | Interest saved | Paid off sooner |
|---|---:|---:|
| $100 a month | $74,741 | 3 yr 11 mo |
| $200 a month | $126,421 | 6 yr 10 mo |
| $500 a month | $219,166 | 12 yr 3 mo |
| One extra payment a year | $114,954 | 6 yr 2 mo |

“One extra payment a year” has the same effect as paying half the monthly amount every two weeks (26 half-payments make 13 full ones), without needing a biweekly plan.

## Before you prepay

**Check these first**

1. **Emergency savings** — Money in the house is hard to get back out quickly. Keep a cash cushion first.
2. **Higher-rate debt** — Paying off a credit card at a higher rate saves more than prepaying the mortgage.
3. **Retirement matches** — An employer match on retirement contributions is usually worth more than mortgage interest saved.
4. **Prepayment penalties** — Some lenders charge a fee if you pay off all or part of the loan early, usually within the first few years. Check your loan documents or ask your servicer.
5. **How the servicer applies it** — Ask for extra money to go to principal, not to next month’s payment, and check your statement.

> **Tip: Extra payments can end PMI sooner**
>
> On a conventional loan you can ask to cancel PMI once your balance reaches 80% of the original value, and it ends automatically at 78%. Prepaying reaches those points earlier.

## Extra payments vs a shorter loan

A 15-year loan forces the faster payoff and usually carries a lower rate — 6.6% versus 7.24% in Freddie Mac’s latest survey — but the higher required payment leaves no flexibility in a tight month. Prepaying a 30-year loan gets part of the benefit while keeping the lower required payment. The [payment calculator](https://mortgage-math-us.com/tools/mortgage-payment-calculator/) compares the two terms side by side.

## Frequently asked questions

### How much do extra mortgage payments save?

It depends on the balance, rate and how early you start. On a $325,000 30-year loan at the current average, $200 a month extra saves about $126,421 in interest.

### Is it better to pay extra monthly or once a year?

Monthly extra saves slightly more because each payment starts reducing interest sooner, but the difference is small. Choose the pattern you can keep up.

### Do biweekly payments pay off a mortgage faster?

Yes, because 26 half-payments equal 13 full payments a year — one extra payment. You can get the same result by adding one-twelfth of a payment each month.

### Does paying extra lower my monthly payment?

No. On most fixed-rate loans the required payment stays the same and the loan ends earlier. Some servicers offer a recast that re-spreads a large lump sum over the remaining term; ask yours about its terms.

### Should I pay off my mortgage early or invest?

Prepaying earns a guaranteed return equal to your mortgage rate. Investing may earn more or less. Many people first build savings and capture any employer retirement match.

## Sources

- [Freddie Mac Primary Mortgage Market Survey](https://www.freddiemac.com/pmms) — 30-year fixed rate, national weekly average; 15-year fixed rate, national weekly average (Week of Oct 29, 2026)
- [US Census Bureau, American Community Survey 2024 1-year](https://data.census.gov/table/ACSDT1Y2024.B25077?g=010XX00US) — Median value of owner-occupied homes (2024 ACS 1-year)
- [CFPB](https://www.consumerfinance.gov/ask-cfpb/when-can-i-remove-private-mortgage-insurance-pmi-from-my-loan-en-202/) — Ask your servicer to cancel PMI at this share of original value; PMI ends automatically at this share of original value (Oct 28, 2026)
- [CFPB](https://www.consumerfinance.gov/ask-cfpb/what-is-a-qualified-mortgage-en-1789/) — Longest term allowed on a Qualified Mortgage (Jan 7, 2025)
- [CFPB: What is a prepayment penalty?](https://www.consumerfinance.gov/ask-cfpb/what-is-a-prepayment-penalty-en-1957/)

_General information, not financial advice._