Amortization Calculator
Generate detailed payment schedules and see the impact of extra payments
How to Use This Amortization Calculator
- Enter your total loan amount
- Input the annual interest rate from your loan agreement
- Select your loan term in years (and additional months if applicable)
- Add any extra monthly, yearly, or one-time payments you plan to make
- Click 'Generate Amortization Schedule' to see your complete payment breakdown
Example: For a $250,000 loan at 6.5% over 30 years, your monthly payment is $1,580. In payment #1, only $227 goes to principal while $1,354 goes to interest. By payment #180 (year 15), it's roughly split 50/50. Adding just $200 extra monthly saves $67,000 in interest and pays off 6 years early.
Tip: Extra payments made in the first years save dramatically more than the same payments made later. Even small amounts compound into major savings.
Why Use a Amortization Calculator?
An amortization calculator reveals exactly where your money goes each month and shows how to strategically reduce interest costs.
- See how much of each payment goes to interest vs principal
- Calculate interest savings from extra monthly payments
- Determine how much faster you'll pay off with annual lump sum payments
- Plan the optimal timing for one-time prepayments
- Compare different loan terms (15 vs 20 vs 30 years)
- Understand why early extra payments have the biggest impact
Understanding Your Results
Your amortization schedule shows the journey from first payment to payoff. Key metrics help you evaluate prepayment strategies.
| Result | Meaning | Action |
|---|---|---|
| Interest > 50% of payment | Early loan phase | Extra payments now provide maximum interest savings |
| Interest = 25-50% of payment | Mid-loan phase | Extra payments still valuable; compare to investment returns |
| Interest < 25% of payment | Late loan phase | Most of payment already reduces principal; investing may beat prepaying |
| Payoff shortened 20%+ | Significant acceleration | Your extra payment strategy is working effectively |
Meaning: Early loan phase
Action: Extra payments now provide maximum interest savings
Meaning: Mid-loan phase
Action: Extra payments still valuable; compare to investment returns
Meaning: Late loan phase
Action: Most of payment already reduces principal; investing may beat prepaying
Meaning: Significant acceleration
Action: Your extra payment strategy is working effectively
Note: The crossover point where principal exceeds interest typically occurs around 60-65% through the loan term for 30-year mortgages at current rates.
About Amortization Calculator
Formula
M = P × [r(1+r)^n] / [(1+r)^n - 1] Where M is monthly payment, P is principal (loan amount), r is monthly interest rate (annual rate / 12), and n is total number of payments. Each month's interest = remaining balance × monthly rate.
Current Standards: Standard amortization assumes equal monthly payments with interest calculated on remaining principal. Prepayments reduce principal directly, which reduces future interest calculations.
Frequently Asked Questions
Why does so much go to interest at the start?
Interest is calculated on your remaining balance. With a $250,000 balance, 6.5% annual interest means about $1,354 monthly interest. As you pay down the balance, less interest accrues, so more of your fixed payment goes to principal. This is why the same $1,580 payment is mostly interest in year 1 but mostly principal in year 30.
What's the best extra payment strategy?
Regular extra monthly payments typically work best because they consistently reduce principal and lower interest every single month. A $200 extra monthly payment on a $250,000 loan at 6.5% saves $67,000 and cuts 6 years off the loan. Lump sum payments work well when you receive bonuses or windfalls.
Should I prepay my mortgage or invest the money?
Compare your mortgage rate to expected after-tax investment returns. If your mortgage is 6.5% and you expect 8% returns (taxable), investing might win mathematically. But prepaying provides guaranteed, risk-free returns and the psychological benefit of faster debt freedom. Many people do both.
Does it matter when in the year I make extra payments?
Yes - earlier is always better. A $5,000 extra payment in January saves more than the same payment in December because you avoid 11 extra months of interest on that $5,000. For maximum impact, make extra payments as early in each month as possible.
How do I ensure extra payments go to principal?
Explicitly specify that extra amounts should apply to principal, not be held for future payments. Most lenders have a field for 'additional principal' on payment forms. Verify this in your account settings or by checking that your balance decreases by the full extra amount.