Use this calculator to estimate your monthly repayment mortgage payment and total interest. Add an optional monthly overpayment to see how quickly you could clear your mortgage balance.
What is a repayment mortgage?
A repayment mortgage is a home loan where each monthly payment includes both interest and principal. That means your balance reduces every month, and if you keep paying as agreed, the loan is fully repaid at the end of the term.
This is different from an interest-only mortgage, where payments only cover interest and the original loan amount still needs to be repaid later.
How this repayment mortgage calculator helps
This tool gives you a practical snapshot of your mortgage numbers:
- Required monthly payment (principal + interest)
- Total amount paid over the term
- Total interest paid
- Estimated payoff date impact if you add overpayments
- A 12-month amortization preview so you can see where your payment goes
The formula behind the monthly payment
For a fixed-rate repayment mortgage, the standard monthly payment formula is:
M = P × r × (1 + r)n / ((1 + r)n - 1)
- M = monthly payment
- P = loan principal
- r = monthly interest rate (annual rate ÷ 12)
- n = total number of monthly payments
If your rate is 0%, payment is simply principal divided by number of months.
How to use the calculator
- Enter your loan amount.
- Enter your annual interest rate.
- Enter the mortgage term in years.
- Add an optional extra monthly payment.
- Click Calculate to view monthly payment, total interest, and payoff details.
Why overpayments can be powerful
With repayment mortgages, interest is calculated on the remaining balance. When you pay extra, your balance drops faster, which reduces future interest charges. Over time, even modest overpayments can save thousands and shorten the mortgage term by years.
Simple overpayment strategies
- Round up your payment (for example, from $1,842 to $1,950).
- Add a fixed monthly overpayment you can sustain comfortably.
- Apply bonuses or side-income chunks directly to principal.
- Increase overpayments after salary increases instead of expanding lifestyle costs.
Costs this calculator does not include
For clarity, this calculator focuses on principal and interest only. Your full housing payment may also include:
- Property taxes
- Homeowners insurance
- Mortgage insurance (PMI/MIP)
- HOA dues
- Closing costs and lender fees
Always compare this estimate with your lender’s official loan illustration.
Common mistakes when planning mortgage repayments
- Ignoring affordability: A bank approval amount is not always a comfortable monthly budget.
- Forgetting variable costs: Taxes and insurance can rise over time.
- Assuming rates stay the same forever: If your rate can reset, future payments may change.
- Overpaying without emergency savings: Keep a cash buffer before committing to aggressive prepayments.
Frequently asked questions
Is this calculator for fixed or adjustable mortgages?
It works best for fixed-rate periods where the interest rate is stable. For adjustable-rate mortgages, recalculate whenever your rate changes.
Can I pay off my mortgage early?
Usually yes, but some loans include prepayment penalties. Check your loan agreement before making large extra payments.
Does making one extra payment per year matter?
Yes. Even one additional monthly payment each year can reduce total interest and shorten the term meaningfully.
How accurate are the results?
Results are strong estimates based on standard amortization math. Your lender’s calculations may vary slightly due to rounding rules, payment timing, and escrow treatment.
Bottom line
A repayment mortgage calculator turns a complicated loan into clear monthly numbers. Use it to test scenarios, compare terms, and build a plan that balances fast payoff with financial flexibility. The best mortgage strategy is one you can sustain consistently, even when life gets busy.