Free workbook · Step-by-step guide
Loan Amortization Schedule
Excel template.
A fixed-rate amortization schedule splits each payment into interest and principal, then updates the remaining balance. This free Excel template adds an optional extra monthly payment and estimates payoff time, total interest, and interest saved.
By Devon Coombs, CPA, MBA · Assistant Teaching Professor of Finance and Faculty Director of Real Estate Finance, Santa Clara University · Guide reviewed October 10, 2026
How do I make a loan amortization schedule with extra payments?
- Enter the starting loan balance, fixed annual rate, and term. The worksheet supports up to 480 monthly payments, or 40 years.
- Start with no extra payment and review the scheduled principal-and-interest payment.
- Add a monthly extra principal payment. Compare payoff time and total interest with the original schedule.
- Confirm how your lender applies extra payments and whether the actual loan has fees or prepayment restrictions.
Worked example
The first payment on a $300,000 loan
- Principal / fixed annual rate / term
- $300,000 / 6% / 30 years
- Monthly principal and interest
- $1,798.65
- First-month interest
- $1,500.00
- First-month principal
- $298.65
The first payment leaves approximately $299,701.35 outstanding. Later payments allocate more to principal as the balance falls.
Know what the model leaves out
The model uses monthly payments and annual rate divided by 12. It excludes property taxes, insurance, mortgage insurance, HOA dues, maintenance, and loan fees. It does not model adjustable rates, irregular payment dates, or interest-only periods. Extra payments generally shorten the modeled term rather than automatically reducing the required payment.
Common questions
Does this spreadsheet show my full monthly housing cost?
No. It calculates loan principal and interest. Add taxes, insurance, HOA dues, maintenance, and any mortgage insurance for an all-in housing budget. The mortgage calculator below includes additional housing-cost inputs.
Will an extra principal payment lower my required monthly payment?
The spreadsheet keeps the scheduled payment and pays the loan off sooner. Whether a lender can recast the required payment depends on the loan and lender rules; that is not modeled here.
Build the next part of your plan
Built as an Excel workbook. If you import it into Google Sheets or Numbers, check formulas and formatting before relying on the results. Devon Coombs Academy is an independent educational resource; these downloads are not an official Santa Clara University product or personalized financial advice.