Last updated October 12, 2026 · Report an error
A mortgage payment looks like one flat number every month, but underneath it the split between interest and principal shifts constantly — early payments are mostly interest, later ones are mostly principal. This calculator finds the monthly payment, total interest over the life of the loan, and a month-by-month amortization schedule showing exactly how that split changes over time.
How it works
Enter the loan amount, annual interest rate, and term. The calculator finds the monthly payment using the standard amortization formula, then walks through the loan month by month, calculating the interest and principal portion of every payment.
- Enter loan amount ($).
- Enter annual interest rate (%).
- Enter loan term (years).
- Click Calculate to see your results.
Examples
A $300,000 loan at 6.5% over 30 years
Monthly payment is $1,896.20, with $1,625.00 of the first payment going to interest and only $271.20 to principal — that split gradually flips as the loan matures.
Who should use it
- Understanding exactly how much of each mortgage payment goes to interest versus principal.
- Comparing total interest cost across different loan terms or interest rates.
Industry applications
- Mortgage lending and real estate
- Personal finance planning
Advantages
- Shows the exact monthly payment plus a real month-by-month amortization breakdown.
- Reports total interest and total paid over the full loan term.
Limitations
- Full schedules for long loan terms are summarized to the first 12 months for readability rather than showing all 360+ rows.
Common mistakes to avoid
- Assuming the interest/principal split stays constant throughout the loan — it shifts substantially from mostly-interest to mostly-principal over time.
- Forgetting that a longer term lowers the monthly payment but increases total interest paid.
Best practices
- Compare the total interest figure (not just the monthly payment) when evaluating different loan terms or extra-payment strategies.
Tips
- Pair this with the Mortgage Payoff Calculator to see how much time and interest an extra monthly payment would save on top of the standard schedule.