What This Calculator Does
A mortgage amortization calculator produces a payment-by-payment map of your entire home loan, showing exactly how each monthly payment is split between interest owed to the lender and principal that reduces your outstanding balance. Amortization is the accounting process by which a fixed-rate loan is paid down in equal installments over a set term — typically 15, 20, or 30 years — with the interest portion of each payment calculated on the remaining balance. Because interest is front-loaded on a fully amortizing mortgage, your earliest payments funnel the majority of every dollar to the lender as interest, while only a small slice chips away at principal. As the balance falls, the interest charge on the next payment shrinks, and a larger share of your fixed payment goes toward principal. By the final years of the loan, nearly every dollar is principal. The schedule this calculator generates is the same document lenders, underwriters, and closing attorneys use. It shows the beginning balance, scheduled payment, interest portion, principal portion, and ending balance for every single month of the loan — often 360 rows for a 30-year mortgage. It also rolls those months up into a yearly view so you can see, at a glance, how much interest you'll pay in year one versus year ten, when you'll cross the 20% equity threshold to drop private mortgage insurance, and the exact month your loan is scheduled to pay off. Whether you're buying your first home, evaluating a refinance, planning extra principal payments, or simply trying to understand what that 30-year commitment really costs, an amortization schedule turns an abstract interest rate into a concrete, dollar-for-dollar plan you can print, save, and reference for the life of the loan.
How It Works
The calculator starts with three numbers you enter: the loan amount (home price minus down payment), the annual interest rate, and the loan term in years. From there it computes a fixed monthly principal-and-interest payment using the standard amortization formula: M = P × [ r(1+r)^n ] / [ (1+r)^n − 1 ] Where M is the monthly payment, P is the loan principal, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (years × 12). For a $320,000 loan at 6.5% over 30 years, that formula yields a monthly principal-and-interest payment of about $2,023 — and that number never changes for the life of a fixed-rate loan, no matter how the balance evolves. Once the payment is fixed, the schedule is built one month at a time. For each row the calculator does three things: (1) multiply the current outstanding balance by the monthly rate to get that month's interest charge, (2) subtract the interest from the fixed payment to get the principal portion, and (3) subtract the principal from the balance to get the new outstanding balance carried into the next month. In month one of the example above, roughly $1,733 goes to interest and only $290 to principal. By month 180 (halfway through a 30-year loan), the split has shifted to roughly $1,190 interest and $833 principal. By the last payment, more than $2,000 goes to principal and just a few dollars to interest. The schedule this tool produces groups those 360 rows into 30 annual summaries so you can quickly see total interest and total principal paid each year, plus the year-end balance. Expand any year and you'll see the individual monthly rows underneath. The summary strip at the top surfaces the four numbers people ask for most: the monthly payment, the original loan amount, the lifetime interest cost (payment × number of payments − loan amount), and the projected payoff date based on the start month you entered. The Print PDF button captures the entire schedule in a clean, borderless layout suitable for your loan file, financial planner, or tax records.
Why It Matters
Most borrowers focus on the interest rate and the monthly payment, but the amortization schedule is where the true cost of a mortgage becomes visible. On a $320,000 loan at 6.5% over 30 years, you'll pay approximately $728,000 in total — meaning more than $408,000 in interest on top of the amount you borrowed. That is more than the original loan itself, and it's hidden in plain sight inside the schedule. Seeing the number in context, spread across 360 rows, changes how borrowers think about extra payments, refinancing, and loan term. The schedule also reveals the equity curve of your home. Equity — the portion of the property you actually own — grows slowly at first because principal payments are small in the early years. A borrower five years into a 30-year loan has typically paid down only about 8% of the original balance, even though they've made 60 payments totaling well over $100,000. This matters when you're evaluating a move, a home equity line, or the point at which you can request PMI removal (typically 20% equity based on original purchase price). The schedule tells you the exact month you cross that threshold. Amortization schedules are also the foundation for every refinance decision. To compare a new loan honestly, you need to know your current remaining balance, how much interest you've already paid, and how much interest you would still pay if you kept the existing loan versus starting a new 30-year term. Without the schedule, those comparisons devolve into monthly-payment math that ignores the fact that a lower payment stretched over a fresh 30 years can cost tens of thousands more in lifetime interest. The schedule turns refinance analysis into an apples-to-apples comparison. Extra-payment strategies live or die by the schedule. A single $200 extra principal payment made in year one of a 30-year loan can eliminate roughly $600 of interest and shave a full month off the end of the loan. Consistent extra payments compound that effect dramatically — often shortening a 30-year loan by five or more years and saving six figures in interest. You can't see, plan for, or credibly commit to that strategy without the schedule in front of you. There is also a tax and estate-planning angle. The interest column, summed by year, is exactly what your lender reports on IRS Form 1098 and what flows onto Schedule A if you itemize. Homeowners in higher tax brackets who itemize can effectively recover a meaningful percentage of their annual mortgage interest — but only if they know what the number is and plan around it. Similarly, when property is transferred, sold, or refinanced as part of a divorce or estate settlement, the remaining balance and accumulated interest on the schedule become critical evidence for equitable distribution, capital-gains basis, and creditor negotiations. For real-estate investors and second-home owners, the schedule doubles as a cash-flow forecasting tool. Because the principal-versus-interest split changes every month, so does the tax-deductible portion of the payment on an investment property and the amount that flows to equity build. Modeling a five- or ten-year hold period against the schedule tells you the exact equity you'll have accumulated at exit, which — combined with projected appreciation — is the foundation of any credible internal-rate-of-return analysis on the deal. Owner-occupants rarely think in those terms, but the schedule enables that same discipline for anyone willing to look at it.
Loan Details
Monthly Payment
$2,023
Loan Amount
$320,000
Total Interest
$408,142
Payoff Date
Jan 2000
| Year | Payments | Principal | Interest | End Balance | |
|---|---|---|---|---|---|
| Year 1 | $24,271.41 | $3,576.72 | $20,694.69 | $316,423.28 | |
| Year 2 | $24,271.41 | $3,816.26 | $20,455.15 | $312,607.02 | |
| Year 3 | $24,271.41 | $4,071.84 | $20,199.57 | $308,535.17 | |
| Year 4 | $24,271.41 | $4,344.54 | $19,926.87 | $304,190.63 | |
| Year 5 | $24,271.41 | $4,635.50 | $19,635.91 | $299,555.13 | |
| Year 6 | $24,271.41 | $4,945.95 | $19,325.46 | $294,609.18 | |
| Year 7 | $24,271.41 | $5,277.19 | $18,994.22 | $289,331.98 | |
| Year 8 | $24,271.41 | $5,630.62 | $18,640.80 | $283,701.37 | |
| Year 9 | $24,271.41 | $6,007.71 | $18,263.70 | $277,693.66 | |
| Year 10 | $24,271.41 | $6,410.06 | $17,861.36 | $271,283.60 | |
| Year 11 | $24,271.41 | $6,839.35 | $17,432.06 | $264,444.26 | |
| Year 12 | $24,271.41 | $7,297.39 | $16,974.02 | $257,146.86 | |
| Year 13 | $24,271.41 | $7,786.11 | $16,485.30 | $249,360.75 | |
| Year 14 | $24,271.41 | $8,307.56 | $15,963.85 | $241,053.19 | |
| Year 15 | $24,271.41 | $8,863.94 | $15,407.48 | $232,189.25 | |
| Year 16 | $24,271.41 | $9,457.57 | $14,813.84 | $222,731.68 | |
| Year 17 | $24,271.41 | $10,090.96 | $14,180.45 | $212,640.72 | |
| Year 18 | $24,271.41 | $10,766.77 | $13,504.64 | $201,873.95 | |
| Year 19 | $24,271.41 | $11,487.84 | $12,783.57 | $190,386.11 | |
| Year 20 | $24,271.41 | $12,257.20 | $12,014.21 | $178,128.90 | |
| Year 21 | $24,271.41 | $13,078.09 | $11,193.32 | $165,050.81 | |
| Year 22 | $24,271.41 | $13,953.96 | $10,317.46 | $151,096.86 | |
| Year 23 | $24,271.41 | $14,888.48 | $9,382.93 | $136,208.38 | |
| Year 24 | $24,271.41 | $15,885.59 | $8,385.83 | $120,322.79 | |
| Year 25 | $24,271.41 | $16,949.47 | $7,321.94 | $103,373.32 | |
| Year 26 | $24,271.41 | $18,084.61 | $6,186.80 | $85,288.71 | |
| Year 27 | $24,271.41 | $19,295.77 | $4,975.64 | $65,992.94 | |
| Year 28 | $24,271.41 | $20,588.05 | $3,683.37 | $45,404.89 | |
| Year 29 | $24,271.41 | $21,966.86 | $2,304.55 | $23,438.03 | |
| Year 30 | $24,271.41 | $23,438.03 | $833.39 | $0.00 |
Savings, if any, vary based on consumer credit profile, interest rate availability, and other factors.
Default rates: Federal Reserve Economic Data (FRED), Freddie Mac Primary Mortgage Market Survey
How Mortgage Amortization Is Calculated
The calculator starts with three numbers you enter: the loan amount (home price minus down payment), the annual interest rate, and the loan term in years. From there it computes a fixed monthly principal-and-interest payment using the standard amortization formula: M = P × [ r(1+r)^n ] / [ (1+r)^n − 1 ] Where M is the monthly payment, P is the loan principal, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of payments (years × 12). For a $320,000 loan at 6.5% over 30 years, that formula yields a monthly principal-and-interest payment of about $2,023 — and that number never changes for the life of a fixed-rate loan, no matter how the balance evolves. Once the payment is fixed, the schedule is built one month at a time. For each row the calculator does three things: (1) multiply the current outstanding balance by the monthly rate to get that month's interest charge, (2) subtract the interest from the fixed payment to get the principal portion, and (3) subtract the principal from the balance to get the new outstanding balance carried into the next month. In month one of the example above, roughly $1,733 goes to interest and only $290 to principal. By month 180 (halfway through a 30-year loan), the split has shifted to roughly $1,190 interest and $833 principal. By the last payment, more than $2,000 goes to principal and just a few dollars to interest. The schedule this tool produces groups those 360 rows into 30 annual summaries so you can quickly see total interest and total principal paid each year, plus the year-end balance. Expand any year and you'll see the individual monthly rows underneath. The summary strip at the top surfaces the four numbers people ask for most: the monthly payment, the original loan amount, the lifetime interest cost (payment × number of payments − loan amount), and the projected payoff date based on the start month you entered. The Print PDF button captures the entire schedule in a clean, borderless layout suitable for your loan file, financial planner, or tax records.
M = L × r(1+r)^n / ((1+r)^n − 1), where L = HomePrice − DownPayment Total Interest = M × n − L Where: L = loan amount, r = monthly rate (annual/100/12), n = loanTerm(years) × 12, M = monthly principal & interest payment. Assumptions: Monthly compounding, fixed-rate fully amortizing loan, no taxes/insurance/PMI/HOA included, payoff date computed by adding n months to the start date.
Key Takeaways
- •Print the schedule immediately after closing and keep it with your loan documents — it's the single most useful reference for future refinance, PMI-removal, and sale decisions.
- •Look at the interest column in year one and year 30 side by side. The dramatic shift illustrates why paying extra principal early is exponentially more valuable than paying extra late in the loan.
- •Use the schedule to identify the month you cross 20% equity based on original purchase price. That is the earliest date you can typically request PMI cancellation in writing from your servicer.
- •Compare the ending balance at the end of year five (or whenever you might move) to your loan amount. The difference is your true principal paydown — often much smaller than borrowers expect.
- •When evaluating a refinance, always compare the remaining interest on your current schedule to the total interest on the proposed new loan, not just the monthly payments.
- •Extra principal payments should always be labeled 'apply to principal' in your servicer's portal. Otherwise many servicers will apply the extra to the next scheduled payment, which does not accelerate payoff.
- •One extra full payment per year (or equivalent bi-weekly payments) typically shortens a 30-year loan by 4 to 6 years and can save $60,000 to $100,000+ in interest at today's rates.
- •The schedule assumes no changes to rate, term, or principal. If you have an ARM, refinance, or make extra payments, regenerate the schedule with updated inputs to keep it accurate.
- •Save a copy of the schedule at each tax season — the annual interest total is what appears on your 1098 and is potentially deductible if you itemize.
- •If your total lifetime interest looks alarming, run the calculator again with a 15-year term. The monthly payment rises, but total interest often drops by 60% or more — a powerful trade-off worth quantifying before you commit to 30 years.
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