Extra payments reduce the principal immediately, so the interest charged every month after is smaller. The earlier you pay extra, the more you save.
How to use the Mortgage with Extra Payments Calculator
- Loan balance
- Interest rate
- Remaining term
- Extra per month
- One-time extra payment
- Month of the one-time payment
- Next payment date
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the loan balance, interest rate, remaining term, extra monthly payment and any one-time payment with the month it is made.
Tips
- Get a written loan estimate and compare the APR, not just the interest rate.
- Include property tax, insurance, HOA fees and maintenance in your monthly budget.
- A larger down payment lowers the payment and can remove mortgage insurance.
- Rates change daily – use a current quote for the most accurate result.
Common mistakes to avoid
- Looking only at the monthly payment instead of the total cost of the loan.
- Forgetting closing costs and fees.
- Assuming home prices always rise.
Inputs explained
| Field | What to enter |
|---|---|
| Loan balance | Amount in your currency |
| Interest rate | In % |
| Remaining term | Units: years, months |
| Extra per month | Amount in your currency |
| One-time extra payment | Amount in your currency |
| Month of the one-time payment | A number |
| Next payment date | A date |
What each result means
- Monthly payment = pmt([Interest rate]÷1200, [Remaining term], [Loan balance])
- New payoff date = addmonths([Next payment date], [Months to pay off with extra payments] – 1)
- Time saved = ([Remaining term] – [Months to pay off with extra payments])÷12
- Total interest without extra payments = [Monthly payment]×[Remaining term] – [Loan balance]
- Total interest with extra payments = ([Monthly payment] + [Extra per month])×[Months to pay off with extra payments] + [One-time extra payment] – [Loan balance]
- Interest saved = [Total interest without extra payments] – [Total interest with extra payments]
Example values
How the main result changes when Loan balance changes and everything else stays at the example values above:
| Loan balance | Interest saved |
|---|---|
| 125,000 | 59,043.29 |
| 187,500 | 69,401.72 |
| 250,000 | 76,163.53 |
| 312,500 | 80,936.46 |
| 375,000 | 84,489.57 |
| 500,000 | 89,431 |
Formula
Balance after a lump sum at month k = balance(k) − lump sumMonths to pay off with extra = nper(i, M + extra, balance)Interest saved = original total interest − new total interestWorked example
Inputs — Loan balance: $250,000; Interest rate: 6.5 %; Remaining term: 25 years; Extra per month: $200; One-time extra payment: $5,000; Month of the one-time payment: 12; Next payment date: 2026-11-24.
Results — Monthly payment = $1,688.02; Months to pay off with extra payments = 225; New payoff date = Mon, July 24, 2045; Time saved = 6.2 years; Total interest without extra payments = $256,405.37; Total interest with extra payments = $180,241.84; Interest saved = $76,163.53.
Frequently asked questions
Do extra payments go to principal?
Yes, if you tell your lender to apply them to principal.
Is it better to pay extra monthly or a lump sum?
Earlier is better; regular extras and lump sums both work.
Are there prepayment penalties?
Rare on U.S. mortgages since 2014 but check your loan terms.
What formula does the Mortgage with Extra Payments Calculator use?
Balance after a lump sum at month k = balance(k) − lump sum.