Amortization Calculator
See how every mortgage payment splits between principal and interest. Find your crossover month, calculate extra payment savings, or compare refinancing options.
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How to Use This Calculator
Amortization Schedule tab
Enter your loan amount, interest rate, and term. The calculator builds a full year-by-year amortization table showing how each payment splits between principal and interest. Click any year row to expand 12 individual months. The crossover month — when principal exceeds interest — is highlighted.
Extra Payments tab
Same inputs plus extra monthly payment, one-time lump sum, and a biweekly toggle. See how much interest you save, how many years you cut, and compare original vs accelerated payoff side by side. If you're paying PMI, getting to 80% LTV faster eliminates PMI too — double savings.
Refinance Comparison tab
Enter your current balance, current rate, remaining term, then the new rate, new term, and closing costs. The calculator finds your breakeven month and net savings over the remaining life of the loan.
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Every input is encoded in the URL. Click Share to send your exact scenario to a mortgage broker, partner, or financial advisor.
The Formula
The standard amortization formula calculates a fixed monthly payment from principal, rate, and term:
Where:
M = monthly payment
P = loan principal (amount borrowed)
r = monthly interest rate (annual rate ÷ 12)
n = total number of payments (years × 12)
Each month:
Interest = Remaining Balance × r
Principal = M − Interest
New Balance = Remaining Balance − Principal
Early payments are mostly interest. Over time, the principal portion grows. The crossover month is when principal first exceeds interest — typically around month 222 for a 6.5% / 30-year loan.
Biweekly payments: 26 half-payments per year = 13 full payments = one extra payment annually, applied directly to principal.
Example
Lisa & Mike — First-time buyers, Austin TX
Lisa and Mike buy a $450K home with 20% down ($90K). Their loan:
The loan
Without extra payments
With $300/mo extra payment
That $300/month extra — roughly one restaurant dinner less per week — saves them $142K in interest and frees them from the mortgage 9 years early.
PMI note: PMI premiums are deductible as mortgage interest starting TY 2026 (OBBBA). Phase-out at AGI >$100K ($50K MFS), fully phased out at $110K ($55K MFS). If you're paying PMI, extra payments that get you to 80% LTV faster also eliminate PMI — double savings.
FAQ
An amortization schedule is a table showing every payment over the life of a loan. Each row breaks the payment into principal (what reduces your balance) and interest (what the lender charges). Early payments are mostly interest; over time, more goes to principal. The schedule shows exactly when you'll own more of your home than the bank does.
The crossover month is the payment where your principal portion first exceeds the interest portion. Before crossover, most of your payment goes to interest. After crossover, most goes to equity. For a 30-year loan at 6.5%, crossover happens around month 222 (year 19). Lower rates push crossover earlier; higher rates push it later.
Extra payments go directly to principal, reducing the balance that accrues interest. On a $360K loan at 6.5% / 30yr, adding $300/month saves about $142,000 in interest and pays off the loan 9 years early. Even $100/month saves over $60,000. The earlier you start, the more you save — because you reduce the principal that compounds.
Not on qualified mortgages (QM). The Dodd-Frank Act (2014, 12 CFR 1026.43) banned prepayment penalties on QM loans, which covers the vast majority of US mortgages. Some non-QM or jumbo loans may still have penalties — check your loan documents. If your loan was originated after January 10, 2014, and is a standard conforming mortgage, you can prepay freely.
It depends on your mortgage rate vs expected investment returns. At 6.5%, extra payments earn a guaranteed 6.5% "return" (risk-free). If you expect stock returns of 8-10%, investing may win mathematically — but only if you actually invest the money and don't spend it. Many people prefer the guaranteed savings and peace of mind of a paid-off home. The right answer is personal, not just mathematical.
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