About the Mortgage Calculator
This calculator works out your monthly home loan installment from the property price, down payment, interest rate, and loan term, using either flat-rate or effective/declining-balance interest — whichever your lender actually uses. It also generates a full year-by-year amortization schedule showing exactly how much of each year's payments goes toward principal versus interest, and how the remaining balance shrinks over the life of the loan. Everything is calculated locally in your browser; this is a planning estimate, not a substitute for your lender's official figures, which may include fees, insurance, or rounding conventions this tool doesn't account for.
Flat vs Effective Rate
Flat rateInterest is calculated on the original loan amount for the entire term — it never decreases even as you pay down the principal. The monthly payment is simple to compute but tends to cost more in total interest.
Effective / declining balanceInterest is calculated only on the remaining balance each month, so the interest portion shrinks over time as you pay down principal. This is the standard method for most mortgages.
Same stated rate, different costA flat rate and an effective rate with the identical headline percentage are NOT equivalent — flat rate typically results in meaningfully more total interest paid over the life of the loan. Compare total interest, not just the percentage.
Which one applies to youIn the US, UK, and Australia, effective/declining balance is the standard method for virtually all mortgages. Flat rate shows up more often on certain personal or auto loans — check your loan agreement if you're unsure which applies.
What this doesn't includeAdmin fees, provision fees, insurance premiums, notary costs, and any promotional/tiered rate changes over the loan term. Ask your lender for the full official simulation before deciding.
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