Extra Mortgage Payment Calculator
See how many years and how much interest an extra monthly payment saves.
Reviewed by the Calculation Machine team · Updated 24 October 2026 · How we check our maths
Your values
ⓘ Live results
- Interest saved
- $86,232.96
- New payoff time
- 22 yr 3 mo
- Time saved
- 7 yr 9 mo
- New monthly payment
- $1,698.88
Quick answer
An extra monthly payment goes straight to principal, so every later month charges interest on a smaller balance and the loan ends early. On a $250,000 balance at 6% with 30 years left, the regular payment is $1,498.88; adding $200 a month pays the loan off in 22 years 3 months and saves $86,232.96 in interest.
What the Extra Mortgage Payment calculator does
Enter your current loan balance, interest rate, years remaining and the extra amount you plan to add each month. The calculator rebuilds the amortization month by month and compares it with your normal schedule, showing the interest saved, the new payoff time and how many years and months come off the loan.
It works for any fixed-rate, fully amortizing loan — a mortgage, car loan, personal loan or student loan — and also answers "when will my loan be paid off?" if you set the extra amount to 0 and use today's balance. The regular payment is calculated from the balance, rate and years you enter, so for the closest match use the figures from your latest statement.
The model assumes the extra is paid every month from now on and applied entirely to principal, with no prepayment penalty. It ignores escrow for taxes and insurance, which does not affect payoff. To see the full year-by-year split of a loan without extra payments, use the amortization calculator.
The formula
Regular payment M = B × r ÷ (1 − (1 + r)⁻ⁿ) Each month: interest = balance × r; balance = balance + interest − (M + E), repeated until the balance reaches 0 Interest saved = (M × n − B) − interest paid with extra payments
| Symbol | Meaning | Unit |
|---|---|---|
| B | Current loan balance | $ |
| r | Monthly interest rate = annual rate ÷ 12 ÷ 100 | decimal |
| n | Months remaining = years remaining × 12 | months |
| M | Regular monthly principal and interest payment | $ |
| E | Extra payment added each month | $ |
This is the standard level-payment amortization used for US fixed-rate mortgages, with the extra applied to principal each month. A biweekly plan (half a payment every two weeks, 26 half-payments a year) equals one extra full payment a year, so you can model it by entering your regular payment ÷ 12 as the extra amount. True biweekly schedules save slightly more because money arrives earlier. Adjustable-rate loans and interest-only periods are not modeled.
Worked examples
Default: $200 extra on a new 30-year loan
A $250,000 mortgage at 6% with the full 30 years remaining and $200 extra each month.
Inputs
- Current balance250000 $
- Interest rate6 %
- Years remaining30 years
- Extra per month200 $
Result
- Interest saved$86,232.96
- New payoff time22 yr 3 mo
- Time saved7 yr 9 mo
- New monthly payment$1,698.88
An extra $200 (about 13% more per month) cuts 7 years 9 months off the loan and saves $86,232.96. Extra payments do the most good early, when most of each payment is still interest.
Aggressive payoff mid-loan
A homeowner with $180,000 left at 6.75%, 22 years remaining, adds $500 a month.
Inputs
- Current balance180000 $
- Interest rate6.75 %
- Years remaining22 years
- Extra per month500 $
Result
- Interest saved$81,572.41
- New payoff time12 yr 3 mo
- Time saved9 yr 9 mo
- New monthly payment$1,810.59
The loan ends in 12 years 3 months instead of 22, saving $81,572.41. Before committing, check that an emergency fund and any higher-rate debts are covered — prepaying a mortgage locks money up in the house.
Biweekly payments modeled as monthly extra
A $320,000 loan at 7% over 30 years has a $2,128.97 monthly payment. Switching to biweekly half-payments adds one payment a year, about $177.41 a month.
Inputs
- Current balance320000 $
- Interest rate7 %
- Years remaining30 years
- Extra per month177.41 $
Result
- Interest saved$109,250.99
- New payoff time23 yr 9 mo
- Time saved6 yr 3 mo
- New monthly payment$2,306.38
One extra payment a year takes 6 years 3 months off and saves $109,250.99. You can get the same effect by adding a twelfth of your payment each month, which avoids fees some biweekly programs charge.
How much different extra amounts save
All rows use a $250,000 balance at 6% with 30 years remaining (regular payment $1,498.88). The savings grow with the extra amount, but each additional dollar saves a little less than the one before because the loan has fewer years left to charge interest.
| Extra per month | Payoff time | Time saved | Interest saved |
|---|---|---|---|
| $100 | 25 yr 6 mo | 4 yr 6 mo | $51,572.44 |
| $200 | 22 yr 3 mo | 7 yr 9 mo | $86,232.96 |
| $500 | 16 yr 5 mo | 13 yr 7 mo | $146,128.41 |
Make sure the extra goes to principal
Servicers do not always apply extra money the way you expect. Some hold it as an early ("prepaid") next payment, which does not reduce interest. When you pay online, use the field marked additional principal, or write "apply to principal" on a check, and confirm the principal balance drops by the extra amount on your next statement.
Most US mortgages taken out since 2014 cannot charge prepayment penalties except in limited cases in the first three years, but check your note or ask your servicer, especially for older loans, car loans and private student loans.
When paying extra is not the best use of money
Every dollar of extra principal earns a guaranteed return equal to your loan rate, but it is hard to get back out. It usually makes sense to cover these first:
- An emergency fund of three to six months of essential costs.
- Any employer 401(k) match — the 401(k) calculator shows its value.
- Credit cards and other debts with higher rates than the mortgage.
If your rate is low compared with what safe savings pay, a lump sum kept in savings may serve you better; if your rate is high, a refinance may beat extra payments.
How to use the Extra Mortgage Payment Calculator
- 1Enter the current principal balance from your latest mortgage or loan statement, not the original loan amount.
- 2Enter the interest rate (not the APR) and the years left on the loan; for 23 years 6 months, enter 23.5.
- 3Enter the extra amount you can add every month. For a biweekly plan, enter your monthly payment divided by 12.
- 4Read the interest saved, new payoff time and time saved. Set the extra to 0 to see your current payoff schedule.
Frequently asked questions
How much faster will I pay off my mortgage with $100 extra a month?
On a $250,000 loan at 6% with 30 years left, $100 extra a month pays it off 4 years 6 months early and saves about $51,600 in interest. Larger balances and higher rates save more.
Is it better to pay extra monthly or one lump sum a year?
The same total paid earlier saves slightly more interest, so spreading it monthly beats one payment at year-end. The difference is small; consistency matters more than timing.
Does paying extra lower my monthly payment?
No. On a standard mortgage the required payment stays the same and the loan simply ends sooner. Some lenders offer a recast, which re-amortizes the lower balance into a smaller payment for a fee.
Do biweekly mortgage payments really save money?
Yes, because 26 half-payments equal 13 full payments a year — one more than monthly. The saving comes from that extra payment, so adding one-twelfth of your payment each month achieves nearly the same result.
Can I use this for a car loan or student loan?
Yes, for any fixed-rate loan with level monthly payments. For student loans, the student loan calculator also shows total repaid.
References
- Ability-to-Repay and Qualified Mortgage Standards (Regulation Z, 12 CFR 1026.43 – prepayment penalties) — Consumer Financial Protection Bureau
- What is a prepayment penalty? — Consumer Financial Protection Bureau
About this calculator
- Built and reviewed by the Calculation Machine team · How we build and test calculators
- Last reviewed: October 24, 2026
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