Mortgage Amortization Explained – How It Works and Why It Matters (2026)
Understanding mortgage amortization is the key to making smarter payments, saving on interest, and knowing when to refinance. This guide explains everything — with examples from USA, UK, Canada, and Australia. By Rajesh Kumar Ram
Most homeowners make monthly mortgage payments for years without truly understanding how those payments are split between interest and principal. The secret is hidden in the mortgage amortization schedule — a table that shows exactly where every dollar goes from your first payment to your last. Understanding amortization is the most important thing you can do to strategically reduce your mortgage cost.
Use our free Mortgage Amortization Calculator to generate your full amortization schedule instantly.
What Is Mortgage Amortization?
Mortgage amortization is the structured repayment of a loan through equal monthly payments over a fixed period. The word "amortize" comes from Old French meaning "to kill" — you are slowly killing the debt over time. Despite equal monthly payments, the split between interest and principal changes with every single payment.
The key insight of amortization: interest is calculated on the remaining balance. Since you start with the full loan amount, early payments are almost entirely interest. As you pay down the balance, progressively more of each payment goes to principal.
How the Amortization Formula Works
Each month, your interest charge = Remaining Balance × Monthly Interest Rate. Your principal payment = Fixed Monthly Payment − Interest Charge.
Month 1 Interest = $300,000 × (7%/12) = $300,000 × 0.5833% = $1,750
Principal Paid = $1,996 − $1,750 = $246
New Balance = $300,000 − $246 = $299,754
Month 2 Interest = $299,754 × 0.5833% = $1,748.60
Principal = $1,996 − $1,748.60 = $247.40...
Notice how principal payment grows by just $1.40 in month 2 — amortization works slowly but accelerates exponentially in the final years of the loan.
Amortization Schedule Example: $300,000 at 7%, 30 Years
| Year | Interest Paid | Principal Paid | Balance Remaining |
|---|---|---|---|
| Year 1 | $20,905 | $3,027 | $296,973 |
| Year 5 | $20,326 | $3,606 | $279,163 |
| Year 10 | $19,380 | $4,552 | $253,731 |
| Year 15 | $17,901 | $6,031 | $218,503 |
| Year 20 | $15,625 | $8,307 | $168,695 |
| Year 25 | $11,993 | $11,939 | $98,115 |
| Year 30 | $3,988 | $19,944 | $0 |
Notice: it takes until approximately Year 22 before the principal paid in a year exceeds the interest paid. This is why homeowners who sell before year 20 have built surprisingly little equity despite years of payments.
How Extra Payments Destroy the Amortization Schedule (In a Good Way)
Extra payments go 100% to principal. This immediately reduces the balance on which future interest is calculated — every extra dollar you pay eliminates compounded interest on that amount for all future months.
On a $300,000 30-year mortgage at 7%, extra monthly payments of:
- $100/month extra: Saves $40,000 in interest, pays off 4 years early
- $200/month extra: Saves $72,000 in interest, pays off 6.5 years early
- $500/month extra: Saves $131,000 in interest, pays off 12 years early
- $1,000/month extra: Saves $175,000 in interest, pays off 17 years early
Use our Mortgage Calculator with Amortization Table to see your exact savings with different extra payment amounts.
Amortization in the UK, Canada, and Australia
Amortization works the same mathematically worldwide, but loan structures vary:
- UK: Interest-only mortgages have no amortization — balance stays the same. Repayment mortgages work like US amortizing mortgages.
- Canada: Amortization up to 25 years (insured) or 30 years (conventional). Canadians often make accelerated bi-weekly payments, which is equivalent to making one extra monthly payment per year.
- Australia: Offset accounts effectively reduce the balance on which interest is calculated, providing a powerful amortization acceleration tool without committing to extra payments.
Frequently Asked Questions
What is mortgage amortization?
It's the structured repayment of a mortgage through equal monthly payments. Each payment covers that month's interest plus some principal. Early payments are mostly interest; later payments are mostly principal.
How do I read a mortgage amortization schedule?
Each row shows: interest paid, principal paid, and remaining balance for each period. In early years, 80%+ is interest. The schedule reveals exactly how much you owe at any point and how much you'd save with extra payments.
What happens to amortization if I make extra payments?
Extra payments go 100% to principal, reducing the balance immediately. This cuts future interest on that balance for all remaining months. $200/month extra on a $300,000 loan at 7% saves ~$72,000 and pays off 6.5 years early.
How is amortization different from a simple interest loan?
In amortizing loans, interest is calculated on the remaining balance (shrinks over time). In simple interest loans, it's calculated on the original amount always. Amortizing loans are cheaper at the same stated rate.
When does negative amortization occur?
When minimum payment is less than monthly interest — balance grows instead of shrinking. Can happen with certain ARM products. Always ensure your payment exceeds the monthly interest charge.