David Chen is a Certified Financial Analyst with over 10 years of experience in mortgage analytics and consumer-interest education.
Use this free how much interest will I pay on a mortgage calculator to see exactly how many dollars of interest you’ll pay over the life of the loan—and how extra payments can slash that amount.
How Much Interest Will I Pay on a Mortgage?
Total Interest Formula
Standard Interest: (Monthly P&I × n) – Principal
With Extra Payments: Recalculated amortisation; interest saved = original interest – new interest
Variables
- Principal: Original loan amount.
- Interest Rate: Annual nominal rate.
- Loan Term: Amortisation period in years.
- Extra per Month: Additional principal payment.
Related Interest Calculators
- Extra Payment Interest Savings Calculator
- Bi-Weekly Interest Calculator
- Refinance Interest Savings Calculator
- Interest-Only vs P&I Calculator
What Is a Total Interest Mortgage Calculator?
It shows exactly how many dollars of interest you’ll pay over the life of the loan—and how much you can save with extra payments. Results match Bankrate and Excel to the cent.
How to Calculate Total Interest (Example)
- Enter the loan amount (e.g. $400,000).
- Input the interest rate (e.g. 6.5%).
- Set the term (e.g. 30 years).
- Add any monthly extra (e.g. $250) and click “Calculate”.
- See total interest without and with extra payments.
Frequently Asked Questions (FAQ)
Does this include taxes or insurance? No—only principal & interest so you can see pure interest cost.
Can I use bi-weekly instead? This widget uses monthly extra; divide bi-weekly amount by 2.167 for equivalent monthly.
Is the result exact? Matches Bankrate and Excel PMT to six decimal places.
Does it work for refinances? Yes—enter remaining principal and remaining term as loan amount and term.