Mortgage Amortization Schedule Calculator
Generate a complete month-by-month amortization schedule for your mortgage. See exactly how much of each payment goes to principal vs. interest, and how extra payments can shorten your loan.
How to Use This Calculator
- Enter your loan amount (principal balance).
- Input your annual interest rate.
- Select the loan term in years.
- Optionally add a monthly extra payment amount.
- Set the loan start date to align the schedule with your payments.
- View the full schedule, yearly summary, and charts showing principal vs. interest over time.
How Amortization Is Calculated
Each monthly payment is split between interest and principal:
Interest portion = Remaining balance × (Annual rate ÷ 12)
Principal portion = Monthly payment − Interest portion
New balance = Previous balance − Principal portion
This process repeats each month. As the balance decreases, less goes to interest and more goes to principal — this is why the split shifts dramatically over time.
Example Scenarios
Standard 30-Year — $300,000 at 6.75%
Monthly P&I: $1,946 · First payment: $1,688 interest + $258 principal
Year 1: $20,183 interest, $3,169 principal paid
Total interest over 30 years: $400,382
With $300/month Extra Payments
Same loan: $300,000 at 6.75%, 30-year
Extra: $300/month toward principal starting month 1
Loan paid off in ~21 years · Interest saved: ~$136,000
15-Year vs 30-Year Comparison
$250,000 loan · 30-yr at 6.75%: $1,621/mo, total interest $333,652
$250,000 loan · 15-yr at 6.0%: $2,110/mo, total interest $129,730
15-year saves $203,922 in interest
Tips for Using Your Amortization Schedule
- Make even small extra payments early — they have the biggest impact on total interest.
- Bi-weekly payments (26 half-payments/year) effectively add one extra payment annually.
- Apply windfalls (tax refunds, bonuses) to principal for accelerated payoff.
- Track your equity growth — it helps with refinancing and HELOC decisions.
- Consider rounding up your payment to the nearest $100 for painless extra principal.
Frequently Asked Questions
What is an amortization schedule?
An amortization schedule is a complete table of every loan payment showing the principal portion, interest portion, and remaining balance. It maps out your entire loan from start to payoff.
Why are early payments mostly interest?
Interest is calculated on the outstanding balance. Since the balance is highest at the start, interest charges are largest early on. On a 30-year loan at 7%, about 80% of your first payment is interest, dropping to under 5% near the end.
How do extra payments help?
Extra payments go entirely to principal, reducing the balance that future interest is calculated on. This creates a compounding savings effect — each extra dollar saves multiple dollars in future interest.
What is principal vs. interest?
Principal is the portion reducing your loan balance (building equity). Interest is the lender's fee for borrowing money. Only principal reduces what you owe.
Can I pay off my mortgage early?
Most conventional loans have no prepayment penalty. Check your loan documents to confirm. If there's no penalty, extra payments are one of the best ways to build wealth through reduced interest costs.