Mortgage Amortization Explained: Why You Pay So Much Interest Early On

In the first year of a $300,000 mortgage at 6.5%, approximately 78% of your monthly payment goes to interest and only 22% goes to reducing your balance. On a $1,896 monthly payment: $1,625 goes to interest, only $271 to principal. By year 15, the split is roughly 50/50. By year 25, most of your payment finally goes to principal. This is why extra payments early in the mortgage have the most impact — every extra dollar reduces the base that interest accrues on for decades.

Here is the real payment split on a $300,000 loan at 6.5% over 30 years. Year 1: $19,504 interest, $3,248 principal (86% to interest). Year 5: $18,541 interest, $4,211 principal (81% to interest). Year 10: $16,838 interest, $5,914 principal (74% to interest). Year 15: $14,432 interest, $8,320 principal (63% to interest). Year 20: $10,975 interest, $11,777 principal (48% to interest). Year 25: $5,911 interest, $16,841 principal (26% to interest). Year 30: $217 interest, $22,535 principal (1% to interest).

This front-loading of interest is why early extra payments are so powerful. An extra $200 per month in year 1 saves approximately $92,000 in total interest because that $200 reduces the principal for the remaining 29 years of compounding. The same $200 extra in year 20 saves only about $12,000 because there are fewer years for the reduced principal to compound. Use the [mortgage payoff calculator](/calculators/mortgage-payoff) to see how extra payments in your specific year affect total interest.

The total cost of a 30-year mortgage is staggering when you see the numbers. On $300,000 at 6.5%: total payments are $682,633. Principal repaid: $300,000. Total interest paid: $382,633. You pay more in interest than the original home price. A 15-year mortgage at 6% on the same loan: total interest drops to $155,683 — saving $226,950. The monthly payment is higher ($2,532 vs $1,896), but the interest savings are enormous. Use the [mortgage calculator](/calculators/mortgage) to compare terms.

How to fight amortization: make extra principal payments as early as possible. Even small amounts compound dramatically. Rounding up your payment from $1,896 to $2,000 saves $56,000 in interest. Biweekly payments effectively add one full extra payment per year. Any windfall (tax refund, bonus, inheritance) applied to principal in the first 10 years has outsized impact. For more strategies, read our guide on [7 ways to pay off your mortgage faster](/blog/how-to-pay-off-mortgage-faster).

Frequently Asked Questions:

Why is amortization structured this way? Lenders calculate interest on the remaining balance. Early in the loan when the balance is highest, interest is highest. As the balance decreases, more of each payment goes to principal.

Can I see my amortization schedule? Yes, most lenders provide one. You can also generate one using the [mortgage calculator](/calculators/mortgage) by entering your loan details.

Is a shorter mortgage always better? Not necessarily. A 15-year mortgage saves massive interest but requires higher monthly payments that reduce cash flow. A 30-year with extra payments gives you flexibility — you can reduce payments during tough months.