Amortization Calculator (2026)
Generate your full loan amortization schedule. See every month's principal vs interest breakdown, total interest paid, and how extra payments slash your payoff date and save thousands.
✏ By AmericaCalculator Finance Team | Updated October 2026 | Works for mortgage, auto, personal, SBA, and HELOC loans
How Loan Amortization Works
When you take out an amortizing loan, your lender calculates a fixed monthly payment that will pay off the entire loan balance over the specified term. This payment consists of two components:
- Interest portion: Calculated as (Annual Rate ÷ 12) × Remaining Balance. In month 1, nearly all your payment goes to interest.
- Principal portion: Payment minus Interest. This reduces your balance and increases each month as the balance falls.
On a $400,000 mortgage at 7.25% (30-year), your monthly P+I payment is $2,729. In month 1, $2,417 goes to interest and only $313 to principal. By month 360, almost the entire payment goes to principal. This is why the early years of a mortgage are so interest-heavy and why paying down principal early has such a dramatic effect.
💡 The Amortization Formula: Monthly Payment = P × [r(1+r)^n] ÷ [(1+r)^n − 1] where P = principal, r = monthly rate (annual/12), n = total number of payments.
How Extra Payments Accelerate Payoff
Extra principal payments have a compounding positive effect because they reduce the balance on which future interest is calculated. Here is how different extra payment amounts affect a $400,000 mortgage at 7.25% (30-year):
| Extra Monthly Payment | Time Saved | Interest Saved | New Payoff |
|---|
| $0 (baseline) | — | — | 30 years |
| $100/month | −2 yr 11 mo | $44,000 saved | 27 yr 1 mo |
| $200/month | −4 yr 8 mo | $78,000 saved | 25 yr 4 mo |
| $500/month | −9 yr 2 mo | $148,000 saved | 20 yr 10 mo |
| $1,000/month | −14 yr 5 mo | $216,000 saved | 15 yr 7 mo |
Biweekly Payments: The Simple Payoff Hack
Making biweekly payments instead of monthly is one of the simplest ways to accelerate payoff with no extra burden. Here is how it works:
- Instead of 12 full monthly payments per year, make 26 half-payments (biweekly)
- 26 × (half-payment) = 13 full payments per year — one extra payment annually
- On a $350,000 mortgage at 7.25%, this cuts the term by approximately 4–5 years
- Total interest savings: approximately $50,000–$60,000 over the life of the loan
- Check with your lender: Ensure they apply biweekly payments immediately to reduce principal, rather than holding them until month-end
Frequently Asked Questions
What is amortization?
Amortization is the process of paying off a loan through scheduled, equal payments over time. Each payment covers both interest (calculated on the remaining balance) and principal (the actual loan reduction). Early in the loan, most of each payment goes to interest. Later, most goes to principal.
How much interest do you pay on a 30-year mortgage?
On a $400,000 mortgage at 7.25% (30-year fixed), you will pay approximately $583,000 in total interest over the life of the loan — more than the original principal. This is why early payoff and extra payments have such dramatic effects.
How much do extra payments save?
On a $400,000 mortgage at 7.25% (30-year), paying an extra $200/month saves approximately $78,000 in interest and cuts 4 years and 8 months off the loan. Paying an extra $500/month saves approximately $148,000 and cuts nearly 9 years.
Is biweekly better than monthly payments?
Yes. Making biweekly payments results in 26 half-payments per year, equivalent to 13 full monthly payments instead of 12. That one extra payment per year reduces a 30-year mortgage by approximately 4–5 years and saves $40,000–$60,000 in interest on a typical $350,000 loan at 7%.
What is negative amortization?
Negative amortization occurs when your monthly payment is less than the interest owed, causing unpaid interest to be added to your principal balance rather than reducing it. Your loan balance grows even as you make payments. This is common in some payment option ARMs and can lead to being deeply underwater on your mortgage.
Does amortization apply to all loans?
Most installment loans amortize: mortgages, auto loans, personal loans, SBA loans, and student loans. Interest-only loans do not amortize during the interest-only period. Credit cards do not amortize in the traditional sense — only the minimum payment is required, not a fixed payoff schedule.
