Set the inputs
Enter the current mortgage balance, remaining term and rate periods. Do not substitute the original house price for the outstanding debt.
Mortgage and overpayments
Model a mortgage with stepped interest rates, overpayments and an explicit interest-rate stress scenario.
Result
Enter your assumptions and calculate payments and remaining debt.
Monthly model: interest and payments round to cents; the final payment clears the balance. Extra payments follow interest and regular payment. Total payments already include extras.
Rate periods and income are your assumptions. Debt-to-income is not a bank approval threshold. A fixed-payment stress scenario that cannot pay off returns an error.
This is an estimate, not a loan offer or an exact lender statement.
How to use this calculator
Check the terms
Set recurring extra payments or lump sums in their payment months. Distinguish a fixed payment from recalculation at a rate reset.
Read the result
Compare payoff month and interest with and without extra payments, then check affordability after a rate change.
A worked example
Illustrative calculation
A 120,000 THB mortgage at 0% over 12 months has a 10,000 THB payment. Adding 2,000 THB monthly clears it in 10 months.
Compare a second scenario
Compare 2,000 THB extra each month with a 24,000 THB annual lump sum in a specified month. Equal amounts reduce the balance at different times.
Common questions
Where does my information go?
Calculations run in your browser. Financial inputs are neither saved locally nor sent to analytics. Reloading restores the initial values.
What are this model’s limitations?
Your rate schedule is an assumption, not a floating-rate forecast. Unentered prepayment penalties and bank-specific terms are excluded.