Mortgage with Extra Payments Calculator
Enter your loan details and any extra payments to instantly see how much interest you save and how many months sooner you pay off your mortgage. The calculator builds a full amortization schedule, a balance-over-time chart, and a step-by-step breakdown of the math so you can see exactly how each extra dollar reduces your loan. It covers monthly extra payments, annual lump sums, and a one-time prepayment, or any combination of the three.
Formula
Worked example
A $300,000 mortgage at 6.5% for 30 years has a monthly payment of $1,896.20. Total interest over 30 years is $382,633. Adding $200/month extra reduces the balance faster: the loan is paid off in about 26 years 2 months (46 months early) and total interest drops to $332,233, saving $50,400.
How extra mortgage payments work
A standard fixed-rate mortgage front-loads interest: in the early years, most of your payment covers interest and only a small slice reduces the principal. When you pay extra and direct it to principal, you shrink the balance on which future interest accrues, which means a larger share of every subsequent payment goes to principal. The effect compounds: the sooner you pay extra, the more you save, because every dollar of principal eliminated today eliminates all the interest it would have generated over the remaining term. That is why paying an extra $200/month from day one saves far more than the same $200/month started in year 10.
Types of extra payments and when to use each
- Monthly extra payment: The most consistent approach. Even $50 or $100/month adds up quickly and is easy to automate. Best for households with steady cash flow who want predictable progress.
- Annual lump sum: Ideal if you receive a year-end bonus, tax refund, or commission. Applying a windfall once a year can shave years off a 30-year mortgage without changing monthly cash flow.
- One-time prepayment: A single large payment, often funded by an inheritance, home equity, or asset sale. The earlier in the loan you make it, the greater the interest saving, because the entire remaining term benefits from the lower balance.
- Combination: Many borrowers pair a modest monthly extra with an occasional lump sum. This calculator handles all three simultaneously.
Reading your amortization schedule
The schedule below shows every payment period: the interest portion (balance x monthly rate), the principal portion (payment minus interest), any extra payment applied that month, and the remaining balance. With no extra payments the balance declines slowly at first and accelerates toward the end. With extras, the balance curve drops faster, which you can see in the chart above. Watch how the "Interest" column shrinks and the "Principal" column grows each month. When extra payments are applied, that shift happens earlier and saves the most money.
Before you make extra payments: things to check
Making extra payments is almost always a good financial move, but check these points first:
- Prepayment penalty: Some mortgages, especially older ones, charge a fee if you pay off the loan early or make extra principal payments above a certain threshold. Read your loan documents or call your servicer.
- Application to principal: Extra money must be applied to principal, not to a future regular payment. Specify "apply to principal" on your payment or in the memo field. Some servicers hold extra funds in a suspense account if you do not specify.
- Higher-rate debt first: If you carry credit card balances at 20% or auto loans at 8%, pay those off before prepaying a 3.5% mortgage. The math strongly favors eliminating higher-rate debt first.
- Emergency fund: Keep 3-6 months of expenses liquid before accelerating mortgage payoff. Equity locked in your home is not accessible in an emergency without refinancing or selling.
Biweekly payments: a common extra-payment strategy
Switching from monthly to biweekly payments is a popular way to make one extra payment per year without feeling it. Because there are 26 biweekly periods per year but only 24 half-monthly periods, you effectively make 13 full payments in 12 months. On a $300,000 mortgage at 6.5%, that one extra annual payment saves roughly $47,000 in interest and cuts the term by about 4.5 years. To replicate this with a monthly setup, add one-twelfth of your monthly payment to each monthly payment, which is the equivalent of the biweekly strategy. This calculator lets you enter that amount in the "extra monthly payment" field for the same result.
Interest saved by extra monthly payment amount (30-year, $300,000 at 6.5%)
| Extra/month | Interest saved | Months saved | New term |
|---|---|---|---|
| $50 | $14,700 | 14 months | 28 yr 10 mo |
| $100 | $27,800 | 26 months | 27 yr 10 mo |
| $200 | $50,400 | 46 months | 26 yr 2 mo |
| $300 | $69,100 | 62 months | 24 yr 10 mo |
| $500 | $99,600 | 88 months | 22 yr 8 mo |
| $1,000 | $149,000 | 130 months | 19 yr 2 mo |
Approximate savings. Actual results depend on your rate, balance, and when you start.
Frequently asked questions
How much do I save by paying an extra $100 a month on my mortgage?
On a $300,000, 30-year mortgage at 6.5%, an extra $100/month saves roughly $27,800 in interest and cuts the loan term by about 26 months. The exact saving depends on your balance, rate, and how early you start: the sooner in the loan life you begin, the more interest each extra dollar eliminates.
Does making extra payments shorten my loan term or lower my monthly payment?
With a standard fixed-rate mortgage, extra payments shorten the loan term, not the monthly payment. Your required payment stays the same until the loan is paid off, but the payoff date arrives sooner. Some adjustable-rate mortgages allow re-amortization (recasting), which would lower the monthly payment after a large lump-sum prepayment, but that requires a formal request and a fee.
Is it better to invest extra money or pay down my mortgage?
It depends on your mortgage rate and the expected return on your investment. If your mortgage rate is 6.5%, paying extra effectively earns you a guaranteed 6.5% after-tax return on that money. If you can reliably invest at a higher after-tax return, investing may come out ahead. However, most personal finance experts recommend keeping an emergency fund, eliminating high-interest debt, and maxing tax-advantaged accounts before making extra mortgage payments.
What is the fastest way to pay off a mortgage?
The fastest legal way is to make the largest extra payments as early as possible. A single large lump sum in year one saves more interest than the same amount paid gradually over 10 years, because it eliminates interest on the entire remaining term. Combining a monthly extra payment with an annual lump sum delivers the most consistent acceleration for typical household budgets.
Will my lender automatically apply extra money to principal?
Not necessarily. Some servicers hold extra funds in a suspense account or apply them to the next monthly payment instead of to principal. Always specify "apply to principal" when making extra payments, either in the payment portal, by check memo, or by calling your servicer. Keep a record and verify on your next statement that the balance dropped by the expected amount.
What is a mortgage prepayment penalty and how do I know if I have one?
A prepayment penalty is a fee charged by the lender if you pay off the loan early or make extra principal payments above a set threshold. They were common on subprime and certain ARMs originated before 2014, but the Dodd-Frank Act restricts them on most new mortgages. Check your loan documents for a "prepayment penalty" clause or call your servicer. If one exists, weigh the penalty against the interest you would save before making large extra payments.
How does biweekly payment differ from an extra monthly payment?
A biweekly schedule splits your monthly payment in half and pays every two weeks. Because there are 26 biweekly periods per year, you end up making 13 full payments instead of 12. The extra payment goes entirely to principal. To mimic this with a monthly schedule, simply add one-twelfth of your regular monthly payment to each monthly payment and mark it for principal. Both strategies produce nearly identical savings.