TL;DR: On a $400,000 loan at 7.03 percent, one $1,000 extra payment in the first month erases $7,093 of interest. The same $1,000 after ten years erases $3,031, and after twenty years about $1,004. Irregular extra payments follow the same curve: starting a year late costs $9,749, and starting ten years late still saves $43,375.
On September 24, 2026, Freddie Mac put the average 30-year fixed at [7.03 percent][5], the highest reading in a year.
For anyone signing a mortgage this fall, the first years are now the most expensive stretch of the loan. They are also the cheapest place to change it.
Most explanations of [mortgage amortization][6] stop at the split. What they leave out is timing. An extra dollar is worth the interest it would have carried for the rest of the loan, and that shrinks every month you wait.
Call it the runway. Every extra dollar erases interest for each month left on the loan, and the runway gets one month shorter with every payment.
How amortization splits the first payment
Take a $400,000 loan at 7.03 percent over 30 years. Principal and interest comes to $2,669.27 a month, and the first payment splits like this:
- Interest: $2,343.33
- Principal: $325.94
That is 88 cents of every dollar going to interest. Run the full term and the interest comes to $560,942, more than the amount borrowed.
When extra payments do the most
One $1,000 extra payment on that loan, sent at four points on the runway:
| When the $1,000 lands | Interest it erases |
|---|---|
| Month one | $7,093 |
| After 5 years | $4,715 |
| After 10 years | $3,031 |
| After 20 years | $1,004 |
In month one, a dollar erases seven dollars of interest. Twenty years in, it erases about one. Nothing about the dollar changed. The runway did.
Extra money rarely arrives on a schedule. Some months carry three small payments, some one, a lean month none, and April brings a $900 tax refund. Say that comes to 20 extra payments and $2,150 over a year.
| That uneven pattern, starting | Time saved | Interest saved |
|---|---|---|
| Month one | 5 years 4 months | $118,331 |
| After 1 year | 5 years | $108,581 |
| After 5 years | 3 years 9 months | $74,821 |
| After 10 years | 2 years 6 months | $43,375 |
Waiting one year to start costs $9,749.
The received wisdom is to settle in for a few years before prepaying. I set my plan before closing in July 2023, when the schedule on $378,000 at 5.625 percent showed $405,353.93 of interest over 30 years. That was not acceptable, and the runway was never going to be longer than that month.
Point to note, the last row is not a consolation prize: $43,375 for starting ten years in. The one exception is order. Card debt and an empty emergency fund come first.
Why the runway is easy to ignore
The math is simple. Seeing it is not.
Your statement reports a balance, never the runway. When extra money goes out as twenty uneven payments a year, the only way to see what they are buying is to [record each one as it happens][3]. Skip the record and the effect goes invisible, and effort you cannot see rarely survives a busy month.
Where PayOff Pro comes in
PayOff Pro does not move your money and does not connect to your bank.
- A payoff date that moves. Log every extra payment, $35 or $900, as it goes out, and watch the projected date step closer.
- What-if scenarios. Test a refund, a bonus, or a few small payments before committing a dollar.
There is no account to create, no sign-in, and no tracking of any kind. Your loan stays on your device.
Three things to do this month
- Send what the budget allows, as often as it allows. Three small payments in a good month and none in a lean one both count.
- Record each payment the day it goes out. A payment you never wrote down is one you cannot see working.
- Confirm it lands on principal. Tell your servicer in writing that extra funds are principal-only, not a prepaid next payment.
The bottom line
You cannot control where rates go after next Thursday's survey. You cannot get back the months already paid.
You can control what this month's extra payments carry, and on a 30-year loan, this month is always the longest runway you have left.
To watch your own payoff date move with every extra dollar, PayOff Pro runs that math on your iPhone: [Get PayOff Pro for iPhone →][1]
3-day free trial, then $9.99 a year or $2.99 a month. No account required, and your loan stays on your device.
Related articles
- [How to Pay Off Your Mortgage Early: The Only Real Way][2]
- [Mortgage Payoff Tracker vs. Calculator: The Posted Balance][3]
- [Mortgage Recast vs. Extra Payments: Comfort or Years Back?][4]
Disclaimer: All figures illustrate a $400,000 loan at 7.03 percent on a 30-year term, with no taxes, insurance, or fees included, and your terms will differ, so verify every number against your own statement before acting. Each $1,000 figure assumes a single extra payment and nothing else extra over the life of the loan. The uneven scenario repeats one twelve-month pattern of 20 extra payments totalling $2,150 a year, and counts each payment in the month it is sent; a different pattern produces a different result. Prepayment rules and how a servicer applies extra funds vary by lender and loan type, so confirm your extra payment reaches principal. This is educational content rather than personalized financial advice, and I am not a financial advisor. PayOff Pro keeps your data on your device, which means your numbers never reach me or anyone else.
[1]: https://apps.apple.com/app/payoff-pro/id6752794539 [2]: /blog/how-to-pay-off-your-mortgage-early-the-only-real-way [3]: /blog/mortgage-payoff-tracker-vs-calculator-the-posted-balance [4]: /blog/mortgage-recast-vs-extra-payments-comfort-or-years-back [5]: https://www.freddiemac.com/pmms [6]: https://www.consumerfinance.gov/ask-cfpb/how-does-paying-down-a-mortgage-work-en-1943/