# Mortgage payoff calculator

> Mortgage payoff calculator: new payoff date, months and interest saved by extra monthly, yearly or one-time payments, or the extra to finish by a date.

Interactive version: https://www.calcopenly.com/finance/mortgage-payoff-calculator
Subject: Finance calculators

The loan is run month by month twice, once at the current payment and once with your extra payments added. Each month's interest is the balance times the annual rate ÷ 12; the payment covers that interest first, and the rest, plus any extra, reduces the principal. The interest saved is the difference between the two schedules. If you know your payment but not the term left, the term is found from the balance, rate and payment.

With the defaults, 300,000 owed at 6.5% with 25 years left, the payment is 2,025.62. Adding 200 a month ends the loan after 243 payments instead of 300, 4 years 9 months early, and saves 68,041.94 of interest. The second mode works backward from a date: finishing 15 years from now takes 587.71 more each month.

The rate is held fixed and each extra amount is applied to principal on its payment date. Escrow for property tax and insurance is left out because it doesn't reduce the balance.

## Inputs

- **Calculate** (options: Extra payments, Payoff by a date)
- **Current loan balance**: Principal still owed, from your latest statement.
- **Interest rate**
- **I know my** (options: Remaining term, Monthly payment)
- **Years left**
- **Plus months**
- **Monthly payment (principal and interest)**: Leave out the escrow part for property tax and insurance; it doesn't reduce the balance.
- **Extra every month**
- **Extra once a year**
- **First yearly extra with payment no.**
- **One-time extra payment**
- **One-time extra with payment no.**
- **Pay off by**
- **Next payment date**

## Results

- New payoff date — main result
- Extra needed each month
- Time saved (months)
- Interest saved
- Current monthly payment
- Monthly payment with extra
- Payments left now
- Payments left with extra
- Current payoff date
- Interest left to pay now
- Interest left with extra payments
- Total extra paid

## Formula

$$
B_k = B_{k-1}(1 + r) - (M + E_k),\qquad \text{saved} = \sum_{\text{current}} I_k - \sum_{\text{with extra}} I_k
$$

## Worked examples

### 372,217.43 left at 6% over 25 years, 500 extra a month

- Calculate: Extra payments
- Current loan balance: 372,217.43
- Interest rate: 6%
- I know my: Remaining term
- Years left: 25 years
- Plus months: 0 months
- Extra every month: 500
- Extra once a year: 0
- One-time extra payment: 0
- Next payment date: in 1 month
- **Current monthly payment: 2,398.20**
- **Payments left with extra: 207**
- **Time saved: 93 months**
- **Interest saved: 122,306.00**
- Checked against: Calculator.net mortgage payoff calculator, published example: paid off in 17 years 3 months, 7 years 9 months earlier, saving $122,306

### 230,000 at 6% paying 1,500, plus 500 a month

- Calculate: Extra payments
- Current loan balance: 230,000
- Interest rate: 6%
- I know my: Monthly payment
- Monthly payment (principal and interest): 1500
- Extra every month: 500
- Extra once a year: 0
- One-time extra payment: 0
- Next payment date: in 1 month
- **Payments left now: 292**
- **Payments left with extra: 172**
- **Time saved: 120 months**
- **Interest left to pay now: 207,677.36**
- **Interest left with extra payments: 113,122.63**
- **Interest saved: 94,554.73**
- Checked against: Calculator.net mortgage payoff calculator, published example (remaining term unknown): 14 years 4 months, 10 years earlier; interest 207,677.36 vs 113,122.63

### Monthly, yearly and one-time extras together

- Calculate: Extra payments
- Current loan balance: 300,000
- Interest rate: 6.5%
- I know my: Remaining term
- Years left: 25 years
- Plus months: 0 months
- Extra every month: 200
- Extra once a year: 2000
- First yearly extra with payment no.: 12
- One-time extra payment: 10,000
- One-time extra with payment no.: 1
- Next payment date: in 1 month
- **Payments left with extra: 200**
- **Time saved: 100 months**
- **Interest saved: 122,421.65**
- Checked against: Python decimal (prec 50) month-by-month loop: 200 every month, 2,000 with payments 12, 24, …, 10,000 with payment 1

### Extra needed to finish by October 2041

- Calculate: Payoff by a date
- Current loan balance: 300,000
- Interest rate: 6.5%
- I know my: Remaining term
- Years left: 25 years
- Plus months: 0 months
- Pay off by: 2041-10-01
- Next payment date: 2026-11-01
- **Extra needed each month: 587.71**
- **Payments left with extra: 180**
- **New payoff date: 2041-10-01**
- **Interest saved: 137,289.63**
- Checked against: Python decimal: 180 monthly payments from 2026-11-01; PMT(6.5%/12, 180, 300,000) = 2,613.3221 minus 2,025.6215, rounded up to the cent

### Extra needed with a known payment, 10-year target

- Calculate: Payoff by a date
- Current loan balance: 230,000
- Interest rate: 6%
- I know my: Monthly payment
- Monthly payment (principal and interest): 1500
- Pay off by: 2036-10-15
- Next payment date: 2026-11-01
- **Extra needed each month: 1,053.48**
- **Payments left with extra: 120**
- **Time saved: 172 months**
- **Interest saved: 131,261.15**
- Checked against: Python decimal: 120 payments before 2036-10-15; PMT(0.5%, 120, 230,000) − 1,500 rounded up to the cent

### Zero-rate loan with 100 extra a month

- Calculate: Extra payments
- Current loan balance: 12,000
- Interest rate: 0%
- I know my: Remaining term
- Years left: 10 years
- Plus months: 0 months
- Extra every month: 100
- Extra once a year: 0
- One-time extra payment: 0
- Next payment date: 2026-11-01
- **Current monthly payment: 100.00**
- **Payments left now: 120**
- **Payments left with extra: 60**
- **Interest saved: 0.00**
- **New payoff date: 2031-10-01**
- Checked against: Hand calculation: 12,000 ÷ 120 = 100; at 200 a month the balance is gone after 60 payments, the 60th on 2031-10-01

## Questions

### How much faster will extra payments pay off my mortgage?

It depends on the rate and the balance, but even small amounts cut years. On 300,000 at 6.5% with 25 years left, the payment is 2,025.62. An extra 100 a month ends the loan 32 months early and saves 38,719.02 of interest; an extra 200 a month ends it 57 months early, 4 years 9 months, and saves 68,041.94.

### How much extra do I need to pay to own my home in 15 years?

Enough to make the payment equal the amount that repays the balance in 180 months. For 300,000 at 6.5%, that payment is 2,613.33, so 587.71 more than the 25-year payment of 2,025.62. It ends the loan 10 years early and saves 137,289.63 of interest. Choose "Payoff by a date" to run your own target.

### Is a yearly lump sum as good as paying extra every month?

Almost, but money paid earlier saves more. On the default 300,000 loan at 6.5%, 100 extra every month saves 38,719.02 and 32 months, while 1,200 paid once a year, starting with the 12th payment, saves 36,951.22 and 31 months. A single 10,000 payment now saves 37,310.10 and ends the loan 23 months early.

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

Yes, because 26 half-payments a year equal 13 monthly payments, one more than the usual 12. To model it, enter your monthly payment as the yearly extra. On the default loan, an extra 2,025.62 once a year ends the loan 48 months early and saves 57,029.51 of interest. Adding one-twelfth of the payment, 168.80, to every monthly payment instead ends it 50 months early and saves 59,673.28.

### Is there a penalty for paying off a mortgage early?

Usually not for extra principal paid in small amounts. The Consumer Financial Protection Bureau says prepayment penalties normally apply when you pay off the whole balance, or a large part of it, within a set number of years, usually three or five. Check your loan documents or ask your servicer before sending a large lump sum.

### How accurate is the mortgage payoff calculator?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 6 worked examples whose answers come from independent sources; for example, “372,217.43 left at 6% over 25 years, 500 extra a month” is checked against Calculator.net mortgage payoff calculator, published example: paid off in 17 years 3 months, 7 years 9 months earlier, saving $122,306.

### Where does the method come from?

Consumer Financial Protection Bureau — What is a prepayment penalty?; Microsoft Excel NPER function (number of payments for a loan); Microsoft Excel PMT function.

## Sources

- [Consumer Financial Protection Bureau — What is a prepayment penalty?](https://www.consumerfinance.gov/ask-cfpb/what-is-a-prepayment-penalty-en-1957/)
- [Microsoft Excel NPER function (number of payments for a loan)](https://support.microsoft.com/office/nper-function-240535b5-6653-4d2d-bfcf-b6a38151d815)
- [Microsoft Excel PMT function](https://support.microsoft.com/office/pmt-function-0214da64-9a63-4996-bc20-214433fa6441)

_Note: financial information, not professional advice._