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Quick answer
What does the Mortgage extra payment calculate?
How much time and interest can overpayments save? This calculator uses mortgage balance, interest rate, remaining term, and extra monthly payment to estimate time and interest saved immediately in your browser.
With the values currently entered, the result is 6y 7m — time saved. It also shows interest saved, new payoff time, and new monthly payment.
How to use the Mortgage extra payment
- Replace the example values with your own numbers.
- Review the result and supporting figures as they update automatically.
- Check the formula and assumptions before using the estimate for a decision.
Inputs used
- Mortgage balance
- Interest rate — entered in %
- Remaining term — entered in years
- Extra monthly payment
Mortgage extra payment formula
Compare amortization with the scheduled payment and with an added monthly overpayment
Assumptions
- The rate remains fixed.
- Extra payments go directly to principal without penalty.
Verify the inputs
Authoritative sources
These sources explain the definitions, factors, or rules behind this tool. Their geographic scope is shown because an official source for one country is not automatically valid somewhere else.
Sources do not endorse Calculum. Check the source date, scope, and your own documents before making a financial, tax, insurance, or reporting decision.
Practical guide
Mortgage extra payment example and edge cases
An extra mortgage payment goes straight to the balance when the lender allows it. That can remove interest and months from the loan.
Example: Adding 300 each month
Start with a 320,000 balance at 6% with 28 years remaining. Add 300 to the scheduled monthly payment.
- Mortgage balance
- 320,000
- Interest rate
- 6 %
- Remaining term
- 28 years
- Extra monthly payment
- 300
Calculated result7y 7mtime saved
Compare the saved interest with other uses for the money. The best choice depends on your cash buffer and other debts.
Example results use the default display profile. The calculator above follows your selected country and units.
How to read the result
- The earlier you make extra payments, the more interest they can avoid.
- Check that the lender applies the money to principal. Some lenders treat it as an early future payment instead.
Edge cases worth checking
There is a prepayment penalty
Subtract the penalty from the estimated saving. Read the loan terms before sending extra money.
The loan has a very low rate
Compare the guaranteed interest saving with your other goals. Liquidity may be more valuable.
What changes the result most
Mortgage balance
Use a current amount for mortgage balance. Include fees or recurring costs that belong in the same figure.
Interest rate
Test a lower and higher interest rate. A small percentage change can move the final result more than expected.
Remaining term
Keep remaining term on the same time basis as the other inputs. Monthly and annual values are easy to mix up.
Try a different scenario
Small changes show whether the answer is stable or sensitive.
Mortgage balance: 10% lower
288,0007y 2mtime saved
Mortgage balance: 10% higher
352,0006y 2mtime saved
Interest rate: 10% higher
7 %6y 11mtime saved
Common mistakes
Check mortgage balance
The rate remains fixed. Make sure this matches the number you enter.
Keep extra monthly payment consistent
Extra payments go directly to principal without penalty. Use the same units and time period throughout the calculation.
Do not rely on one mortgage extra payment scenario
Run a cautious case and an optimistic case. The range is often more useful than one exact-looking number.
Use this result well
How much time and interest can overpayments save?
It cannot replace a lender quote, lease, survey, or purchase contract.