Extra payments go straight to principal, and every dollar of principal you remove stops charging interest for the rest of the loan. On a $300,000, 30-year mortgage at 6.5%, paying just $100 extra a month from the start saves about $61,000 in interest and ends the loan 4 years early. An extra $500 a month saves about $180,000 and cuts 12 and a half years. The earlier you start, the larger the savings, because the money has more months to avoid interest.
The baseline loan
| Detail | Value |
|---|---|
| Loan amount | $300,000 |
| Rate and term | 6.5% fixed, 30 years |
| Monthly principal and interest | $1,896.20 |
| Total interest if paid as scheduled | $382,633 |
Interest each month is the balance × 6.5% ÷ 12, so the formula that matters is:
Each extra dollar lowers every future month’s interest, and those savings snowball because more of each regular payment then goes to principal too. For the payment math itself, see how to calculate mortgage interest.
Savings by strategy
All scenarios start in month 1 unless noted:
| Strategy | Payoff time | Total interest | Interest saved | Time saved |
|---|---|---|---|---|
| No extra payments | 30 years | $382,633 | — | — |
| $100 extra per month | 26 years | $321,639 | $60,995 | 4 years |
| $200 extra per month | 23 years 1 month | $279,185 | $103,449 | 6 years 11 months |
| $500 extra per month | 17 years 6 months | $202,874 | $179,759 | 12 years 6 months |
| One extra payment each year ($1,896.20 in month 12, 24, …) | 24 years 4 months | $298,649 | $83,985 | 5 years 8 months |
| Biweekly equivalent ($158.02 extra per month) | 24 years 2 months | $295,377 | $87,256 | 5 years 10 months |
| $10,000 lump sum in month 1 | 27 years 3 months | $329,032 | $53,602 | 2 years 9 months |
| $10,000 lump sum in month 121 (year 11) | 28 years 6 months | $357,941 | $24,692 | 1 year 6 months |
| $200 extra per month starting in year 11 | 26 years 7 months | $342,976 | $39,658 | 3 years 5 months |
Run your own loan through the mortgage payoff calculator, which rebuilds the schedule with any extra amount.
Three patterns in the numbers
1. Timing matters as much as amount
The same $10,000 lump sum saves $53,602 if paid in month 1 but only $24,692 if paid in year 11, because early in the loan the balance is largest and the money has 29 more years of interest to avoid. Likewise, $200 a month started in year 11 saves less than half of what it saves when started on day one.
2. Spreading extra monthly beats saving it up
A 13th payment made at the end of each year saves $83,985. Paying the same total, one-twelfth of a payment, each month saves $87,256. The difference is small but free: money applied sooner reduces interest sooner.
3. Biweekly is just a 13th payment in disguise
Paying half the monthly payment every two weeks produces 26 half-payments, or 13 full payments, a year. Its effect is about the same as the “$158.02 extra per month” row. The biweekly mortgage calculator models the exact timing. Some companies charge setup or per-payment fees to run a biweekly program for you; there is no need to pay for something you can do yourself by adding one-twelfth of your payment each month.
Easy ways to find the extra money
You do not need a big budget overhaul to get most of these savings:
- Round up the payment. Paying $2,000 instead of $1,896.20 adds $103.80 a month, enough to land close to the $100 row above.
- Send raises to the mortgage. When your pay rises, add part of the increase to the payment before it gets absorbed into spending.
- Use the “extra” paychecks. If you are paid biweekly, two months a year have three paychecks. Sending most of one of those to principal works like a 13th payment.
- Apply windfalls. Tax refunds, bonuses or a paid-off car loan’s old payment can go straight to principal.
- Automate it. Add the extra amount to your recurring payment so it happens without a monthly decision.
The return on prepaying
Prepaying a mortgage earns a guaranteed, tax-free “return” equal to the loan’s interest rate, 6.5% in this example, because every dollar you prepay avoids 6.5% a year of interest. That makes it a sound choice when the rate is high. Compare it with alternatives:
| Use of extra $200 a month | Expected return | Risk | Liquidity |
|---|---|---|---|
| Credit card payoff | The card APR, often 20%+ | None | Low (once paid) |
| 401(k) up to the employer match | Immediate 50% to 100% match, plus growth | Market risk | Low until 59½ |
| Mortgage prepayment | The mortgage rate | None | Very low; equity is hard to tap |
| High-yield savings | Current savings rate | None | High |
| Diversified investing | Variable; historically higher over long periods | Market risk | High in a taxable account |
A common priority order is: emergency fund, full 401(k) match, high-interest debt, then decide between extra mortgage payments and additional investing based on the mortgage rate and your comfort with risk. The investment calculator helps estimate the investing side. If your mortgage rate is 3%, prepaying is a weak use of money; at 7%, it is competitive with many investments, risk-free.
Before you prepay
- Check for a prepayment penalty. Federal rules since 2014 restrict them on most residential mortgages, but confirm in your note.
- Keep an emergency fund. Money paid into the house cannot easily be taken back out without a new loan.
- Tell the servicer it is principal. Label the extra as “additional principal” and verify it on the next statement.
- Consider a recast if you make a large lump-sum payment and want a lower required payment rather than an earlier payoff.
- Watch PMI. Extra payments can bring forward the date you reach 20% equity, when you can ask to cancel private mortgage insurance; it ends automatically at 22% equity based on the original schedule.
Payoff early or keep a long term?
Choosing a 30-year loan and prepaying keeps a low required payment as a safety net, while a 15-year mortgage locks in the faster payoff and usually a lower rate. The amortization calculator lets you compare both schedules row by row.
These are illustrative calculations for education, not financial advice. Results depend on your loan terms and servicer's payment-application rules; review your mortgage note and statements before changing how you pay.
Frequently asked questions
How much does an extra $100 a month save on a mortgage?
On a $300,000, 30-year loan at 6.5%, paying $100 extra every month from the start saves about $61,000 in interest and pays the loan off 4 years early. The savings are larger at higher rates and smaller if you start later in the loan.
Is it better to make one extra payment a year or pay extra monthly?
Paying the same total extra spread monthly saves slightly more, because each dollar reduces the balance sooner. One extra full payment a year on the example loan saves about $84,000; paying one-twelfth of a payment extra each month saves about $87,000.
Do biweekly mortgage payments really save money?
Yes, because 26 half-payments equal 13 full payments a year, one more than the monthly schedule. On the example loan that saves about $87,000 and roughly 6 years. Avoid paid third-party biweekly programs; you can get the same result by adding one-twelfth of a payment to each monthly payment.
Will extra payments lower my monthly payment?
Not automatically. On a standard fixed-rate loan, extra principal shortens the term but the required payment stays the same. Some lenders offer a recast, which re-amortizes the loan after a lump-sum payment to lower the payment, usually for a fee.
How do I make sure extra money goes to principal?
Mark the extra amount as additional principal when you pay online or on the coupon, and check the next statement. If a servicer holds it as an unapplied payment or applies it to the next month's payment, contact them; the CFPB accepts complaints about servicing errors.