Your mortgage amortization schedule reveals exactly where every payment goes—how much reduces your debt vs. how much goes to interest. This calculator generates a complete payment-by-payment breakdown of your entire mortgage.
How This Calculator Works
This calculator creates your complete mortgage schedule:
- Loan Amount: Your mortgage principal
- Interest Rate: Annual rate (APR)
- Term: Loan length in years
- Extra Payments: Optional additional principal
- Amortization Table: Every payment detailed
- Payoff Date: When you'll be mortgage-free
The Formula Explained
Monthly Payment = P × [r(1+r)^n] / [(1+r)^n - 1]
For each payment: Interest Portion = Remaining Balance × (Rate / 12) Principal Portion = Payment - Interest Portion
Early payments are primarily interest; this shifts toward principal over time.
Step-by-Step Example
$400,000 Mortgage at 6.5% for 30 Years
| Payment | Principal | Interest | Balance |
| #1 | $362 | $2,167 | $399,638 |
| #60 (Yr 5) | $480 | $2,049 | $375,140 |
| #180 (Yr 15) | $835 | $1,694 | $309,300 |
| #300 (Yr 25) | $1,455 | $1,074 | $196,640 |
| #360 (Final) | $2,525 | $4 | $0 |
Total: $910,630 (Principal $400,000 + Interest $510,630)
Frequently Asked Questions
What is mortgage amortization?
Amortization is how your mortgage is gradually paid off through scheduled payments over time. Each payment covers interest on the current balance plus a portion of principal. The schedule shows this breakdown for every payment, revealing how your balance decreases month by month.
Why is so much of my early payment interest?
Interest is calculated on remaining balance. With a high balance early on, more interest accrues. Your fixed payment first covers this interest; the rest reduces principal. As balance drops, less goes to interest and more to principal. This is why extra payments early have outsized impact.
How do I read an amortization schedule?
Each row shows: Payment number, payment amount, principal portion, interest portion, remaining balance. Watch how the principal/interest split changes over time. The total interest row shows your complete borrowing cost—often surprising people.
How much interest will I pay over my mortgage?
On a typical 30-year mortgage, you'll pay roughly 80-100% of your principal in interest. A $400,000 mortgage at 6.5% costs ~$511,000 in interest—more than the home price! Higher rates and longer terms increase this dramatically.
How can I save on interest?
Strategies: (1) Make extra principal payments—even $100/month saves tens of thousands. (2) Choose shorter term (15-year vs 30-year)—higher payment but massive savings. (3) Refinance to lower rate when available. (4) Biweekly payments—equals one extra monthly payment/year.
What are extra principal payments and how do they help?
Extra payments go directly to principal, reducing your balance immediately. This: (1) Reduces future interest calculations, (2) Shortens your loan term, (3) Builds equity faster. $200 extra monthly on a $400,000 mortgage at 6.5% saves $124,000 in interest and pays off 6.5 years early!
How does a 15-year compare to a 30-year mortgage?
30-year: Lower payments, more flexibility, but much more total interest. 15-year: Higher payments (roughly 40% more), but typically lower rate and dramatically less total interest. A $400,000 mortgage costs ~$510K interest over 30 years vs ~$180K over 15 years—savings of $330K!
What happens if I sell before the mortgage is paid off?
When you sell, you pay off remaining mortgage balance from sale proceeds. The difference is your equity. Early in the mortgage, equity is mostly your down payment plus any appreciation. Later, more equity comes from paid principal. Check your amortization schedule to see current equity position.
Key Points to Remember
- Interest front-loaded: Most early payments go to interest, not principal
- Extra payments compound: Each extra dollar reduces future interest
- 30-year doubles the cost: Interest often exceeds the home price
- 15-year saves massively: Higher payments but much less total cost
- Review your schedule: Know exactly where you stand on equity