Principal vs Interest Split Calculator
See exactly how much of your next mortgage repayment goes towards paying down the principal versus covering interest charges.
Your results
Calculation breakdown
- Interest this period
- balance × monthly rate
- Principal this period
- repayment − interest
Worked example
On a $480,000 balance at 6% with a $3,000 monthly repayment, about $2,400 covers interest and $600 reduces the principal.
Assumptions
- Shows the split for a single repayment based on the balance entered, not the whole loan term.
How this calculator works
This calculator breaks a single mortgage repayment into its principal and interest components based on your current balance and interest rate, illustrating how the split shifts more towards principal as the loan is paid down over time.
Frequently asked questions
Why is the interest portion higher early in the loan?
Interest is calculated on the outstanding balance, which is largest at the start of the loan, so a bigger share of each early repayment covers interest rather than principal.
Does this calculator project the whole loan term?
No, it shows the split for a single repayment period based on the balance you enter; use the amortisation calculator to see the split over the full loan term.
Will extra repayments change this split?
Extra repayments reduce the balance faster, which lowers the interest portion of future repayments and increases the share going to principal.
Results are estimates only and are not financial, tax, legal or credit advice.