Property
Mortgage Payoff Calculator
Enter your mortgage balance, rate and remaining term to compare payoff time and interest with monthly extra payments or a lump sum. These extra payments are also called overpayments.
Your details
Enter your details below
Your result
Based on the values you enter
Useful next checks
- Check the inputs before relying on the result.
- Try a second scenario to compare outcomes.
- Read the guide below for context.
Intro
Use this mortgage payoff calculator to compare your current repayment plan with monthly extra payments, a one-off lump sum, or both. Extra payments are also called mortgage overpayments in the UK. Enter your balance, rate and remaining term to estimate payoff time, time saved and interest saved.
What this mortgage payoff calculator does
The calculator compares two repayment scenarios:
- Your current mortgage repayment path.
- The same mortgage with a monthly overpayment, a one-off overpayment, or both.
It shows the estimated new payoff time, time saved, interest saved, and total interest under each scenario.
How it works
The calculator models the mortgage month by month. A one-off lump sum reduces the balance at the start of the selected month, before interest is calculated. Each month it then adds interest, applies your normal payment and applies any monthly overpayment from the selected start month.
If you leave the current monthly payment as zero, the calculator estimates a standard repayment using the mortgage balance, annual interest rate, and remaining term. If you enter your own monthly payment, that payment is used for both the current and overpayment scenarios.
Example calculation
Suppose you have a mortgage balance of 200,000, an interest rate of 5%, and 25 years remaining. The standard monthly repayment is estimated from those inputs.
If you add a 200 monthly overpayment from the first month, the calculator reduces the balance faster. Because the balance falls sooner, less interest is charged in later months, which can shorten the mortgage and reduce total interest.
How to use the result
Use the result to test different overpayment plans before speaking to your lender. Try smaller and larger monthly overpayments, or compare a one-off lump sum with a regular payment.
Before making an overpayment, check whether your mortgage has an annual overpayment allowance, early repayment charge, product fee, or minimum overpayment amount.
Assumptions and limitations
- The calculator assumes a fixed interest rate for the full term entered.
- It does not include early repayment charges or lender fees.
- It assumes overpayments reduce the balance rather than lowering future monthly payments.
- It does not model offset mortgages, interest-only mortgages, or payment holidays.
- Payoff time is a duration in years and months, not a calendar payoff date.
- You can use US dollars or UK pounds through the region selector. It changes currency labels, not your entered amounts or the model.
- The result is an estimate, not a lender statement.
Frequently asked questions
Should I overpay monthly or as a lump sum?
Earlier overpayments usually save more interest because the balance falls sooner, but fees and cashflow matter.
Does this change my contractual payment?
The calculator assumes your normal payment stays the same and the extra amount reduces the balance.
What if my rate changes later?
Run a separate scenario with the new rate and remaining term.
Does this include early repayment charges?
No. Check your mortgage deal for overpayment limits, early repayment charges, and product fees before acting.
What if I enter my current monthly payment?
The calculator uses that payment for both scenarios. If you leave it as zero, it estimates a standard repayment from the remaining term.
When is the lump sum applied?
The one-off overpayment is applied in the selected start month before that month's interest is calculated.